Variable stiffness compliant grasping device based on Archimedean spiral principle

Abstract

The variable stiffness compliant gripping device based on the Archimedean spiral principle belongs to the field of mechanical structure design. Existing flexible grippers are unable to grip heavy objects, while flexible grippers with control technology have low operating efficiency and are sensitive to the working environment. A DC motor drives the top-level clamping jaw assembly located on the clamping jaw base to open or close through a driving mechanism; after each upper swing arm is buckled with a lower swing arm, each is connected to a spring mounting frame through a spring to form a swing arm assembly. The lower swing arms in the two swing arm assemblies always remain parallel and are installed in opposite directions. The head ends of the two lower swing arms are rotatably connected to the surface of the drive disk, and the two spring mounting frames are both fixed to the surface of the drive disk; the transmission rocker is a T-bar, and the two ends of the horizontal bar of the T-bar are connected to a slider, each slider slides in the grooves in the upper and lower swing arms, and the vertical bar of the T-bar extends out of the drive disk and is fixedly connected to the top left clamping jaw arm. The present invention is used for compliant gripping of objects.

Description

Technical Field

[0001] The invention relates to a flexible grasping device and belongs to the field of mechanical structure design. Background Art

[0002] Traditional robot grippers are commonly found in grasping devices installed at the end of a robotic arm. They are usually composed of rigid components and are often rigidly connected to the object being grasped. Although such gripping devices are widely used, they generally lack sufficient flexibility. For example, in the industrial and agricultural fields, if you try to use them to grasp fragile objects (such as glassware, fruit, etc.), it is likely to cause damage and destruction to the grasped object. In order to meet the needs of various complex and changeable handling, adjustment and other operations, the flexibility of the gripper can be appropriately adjusted to enable it to adapt to objects of various forms, thereby broadening its application scope and usage scenarios.

[0003] Due to its excellent flexibility, the flexible gripper can effectively prevent damage to the grasped object when grasping fragile objects. For example, in the field of medical rehabilitation, compared with traditional rigid instruments, flexible instruments can minimize secondary injuries to patients during the rehabilitation process. Purely flexible grippers are generally made of flexible materials (such as silicone) and achieve the grasping function through pressure deformation. However, when grasping heavier objects, when the flexible gripper cannot withstand the gravity of the clamped object, it may cause it to slip, and then lead to the failure of the clamping action. In addition, grippers with precise driving technology and sensing elements to achieve the purpose of flexibility require the use of precise control technology and special materials. They are expensive, have low operating efficiency and are sensitive to the working environment, resulting in low cost performance and poor stability. They are not suitable for small and medium-sized industrial and agricultural production scenarios with complex environments. Summary of the Invention

[0004] The purpose of the present invention is to solve the problem that existing flexible clamps are unable to clamp heavy objects, and flexible clamps with control technology have low operating efficiency and are sensitive to the working environment, resulting in low cost performance and poor stability. A variable stiffness flexible grasping device based on the Archimedean spiral principle is proposed.

[0005] A variable stiffness compliant gripping device based on the Archimedean spiral principle includes a DC motor, a drive mechanism, a gripper base, and a top gripper assembly; the top gripper assembly includes a top left gripper arm and a top right gripper arm, the top left gripper arm and the top right gripper arm having identical structures, and the drive ends of the two grippers meshing;

[0006] The DC motor drives the top jaw assembly located on the jaw base to open or close through the drive mechanism;

[0007] The driving mechanism includes a driving plate, a transmission rocker, and two lower swing arms, two spring mounting brackets, two springs, a slider and two upper swing arms arranged inside the driving plate;

[0008] Two lower swing arms, two spring mounting brackets, and two springs are all set inside the drive disc. After each upper swing arm is buckled with a lower swing arm, each is connected to a spring mounting bracket via a spring to form a swing arm assembly. The lower swing arms in the two swing arm assemblies always remain parallel and are installed in opposite directions. The head ends of the two lower swing arms are rotatably connected to the drive disc surface, and the two spring mounting brackets are fixed to the drive disc surface.

[0009] The transmission rocker is a T-shaped rod, with a slider connected to each end of the horizontal rod of the T-shaped rod. Each slider slides in the groove in the upper swing arm and the lower swing arm. The vertical rod of the T-shaped rod extends out of the drive plate and is fixedly connected to the top left clamping claw arm.

[0010] Preferably, the top left clamping arm and the top right clamping arm each include a clamping upper arm, a clamping middle arm and a clamping lower arm;

[0011] The clamping arm of the top left clamping arm and the clamping arm of the top right clamping arm are both arranged on the upper surface of the clamping base, and one end of the two clamping arms serves as the driving end of the corresponding top left clamping arm and the top right clamping arm for engagement;

[0012] The vertical rod of the T-shaped rod extends out of the driving disk and is fixedly connected to the clamping arm of the left clamping arm of the top layer. The other end of each clamping arm is fixedly connected to one end of a clamping small arm. One end of the two clamping middle arms is symmetrically arranged on the upper surface of the clamping base along the meshing line, and the two clamping middle arms are both rotatably connected to the clamping base; the other end of each clamping middle arm is rotatably connected to the middle part of each clamping small arm.

[0013] Preferably, the device further comprises a transmission shaft and a bottom jaw assembly;

[0014] The bottom clamp assembly includes a bottom left clamp arm and a bottom right clamp arm; the bottom left clamp arm and the bottom right clamp arm have the same structure as the top left clamp arm or the top right clamp arm; the bottom left clamp arm and the top left clamp arm are arranged opposite to each other, and the bottom right clamp arm and the top right clamp arm are arranged opposite to each other;

[0015] The bottom left gripper arm and the bottom right gripper arm are both arranged on the lower surface of the gripper base, the bottom left gripper arm and the bottom right gripper arm are meshed, the bottom left gripper arm and the top left gripper arm are connected by a transmission shaft, and the two move synchronously, the bottom right gripper arm and the top right gripper arm are connected by a transmission shaft, and the two move synchronously.

[0016] Preferably, the device further comprises a No. 1 connecting rod, a No. 2 connecting rod and a No. 3 connecting rod;

[0017] The top left gripper arm, the top right gripper arm, the bottom left gripper arm and the bottom right gripper arm all include a gripper upper arm, a gripper middle arm and a gripper lower arm;

[0018] The upper jaw arm of the left clamping arm of the top layer and the upper jaw arm of the right clamping arm of the top layer are both arranged on the upper surface of the clamping base, and one end of the two clamping arms are meshed. The upper jaw arm of the left clamping arm of the bottom layer and the upper jaw arm of the right clamping arm of the bottom layer are both arranged on the lower surface of the clamping base, and one end of the two clamping arms are meshed.

[0019] The gripper arm of the right gripper arm of the bottom layer is connected to the gripper arm of the right gripper arm of the top layer via a transmission shaft, and the right gripper arm of the bottom layer is connected to the right gripper arm of the top layer via a transmission shaft;

[0020] The vertical rod of the T-shaped rod extends out of the driving disk and is fixedly connected to the clamping arm of the left clamping arm of the top layer. The other end of each clamping arm is fixedly connected to one end of a clamping arm. The two clamping arms on the same side are connected by a No. 1 connecting rod, and the two No. 2 connecting rods pass through the clamping base, and the two No. 2 connecting rods are symmetrically arranged along the meshing line. The two ends of the two No. 2 connecting rods are respectively exposed to the upper and lower surfaces of the clamping base, and one end of the two clamping middle arms on the same side is respectively mounted on the two ends of a No. 2 connecting rod on the same side, and the clamping middle arm is rotatably connected to the No. 2 connecting rod, and each No. 3 connecting rod passes through the middle of the two clamping arms on the same side, and the two ends of each No. 3 connecting rod are exposed on the surface of the two clamping arms, and the other ends of the two clamping middle arms on the same side are respectively mounted on the two ends of the No. 3 connecting rod on the same side, and the clamping middle arm is rotatably connected to the No. 3 connecting rod.

[0021] Preferably, the middle arms of the four clamping jaws are telescopic structures with adjustable lengths.

[0022] Preferably, the device further comprises a controller and a serial communication module;

[0023] The controller is used to control the operation of the DC motor through the serial communication module.

[0024] Preferably, the device further comprises 2 spacers;

[0025] A gasket is provided between the head ends of the two lower swing arms and the drive disc.

[0026] The beneficial effects of the present invention are:

[0027] During operation, a DC motor rotates the drive plate, which is fixed to it, about its central axis. This drives the swing arm to swing, causing the spring to extend, changing the system stiffness and controlling the gripping force of the jaws during opening and closing. The swing arm and the spring connection move in an Archimedean spiral. As the swing arm swings, the upper and lower sliders slide relative to each other within the groove, driving the transmission rocker to rotate about its central axis. This further causes the jaw arm to move in a planar manner, tightening the jaws.

[0028] The present invention adopts a stiffness adjustment mechanism design to achieve continuous adjustment of the gripper stiffness, ensuring smooth gripping;

[0029] The present invention adopts a simple transmission mechanism, optimizes the energy transmission path, and reduces energy loss.

[0030] The present invention has a compact structure and high integration, reduces the volume and weight of the device, improves space utilization, and is convenient for integrated application.

[0031] The present invention has an efficient and long-lasting optimized design, which reduces downtime caused by frequent maintenance or replacement of parts, has low maintenance costs, and enhances environmental adaptability and stability.

[0032] The variable stiffness principle of the present invention is to control the clamping jaws through mechanical structural design, thereby achieving rapid and continuous changes in the clamping jaw stiffness, ensuring a grip with high compliance and high clamping force; the device can provide stable clamping force while ensuring compliance. The transmission mechanism of the present invention is simple, the DC motor is fixedly connected to the drive mechanism, and the drive mechanism and its transmission rocker are fixedly connected to the clamping jaw arm on the central axis of the disk, reducing energy loss and achieving high energy utilization; the mechanical structure design of the present invention is simple, reducing costs, and making it more suitable for small and medium-sized industrial and agricultural needs. At the same time, the highly integrated compact design can reduce volume and weight, and improve space utilization; the quickly replaceable clamping jaw interface improves the versatility and flexibility of the gripping device; through optimized design and the selection of high-strength materials, the maintenance cost of the present invention is reduced, the environmental adaptability is enhanced, and it can adapt to complex and changing industrial and agricultural environments, thereby improving the stability of the clamping effect, making it have significant economic benefits and practical value in actual applications. In addition, it is simple to manufacture and cost-effective, and is suitable for the actual needs of a variety of industrial and agricultural production environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A diagram showing the structure of a single-layer gripper of a gripping device;

[0034] Figure 2 It is a structural diagram of the double-layer gripper of the grasping device;

[0035] Figure 3 The exploded diagram of the driving mechanism;

[0036] Figure 4It is a functional diagram of the connection between the gripping device and the end of the freedom robot arm;

[0037] Figure 5 This is a schematic diagram of the gripping device drive mechanism (some parts have been made transparent);

[0038] Figure 6 This is a working diagram of the grabbing device;

[0039] Figure 7 This is a graph showing the relationship between the output torque of the driving mechanism and time at a constant speed;

[0040] Figure 8 This is a diagram of the structural composition of the arm in the gripper. DETAILED DESCRIPTION

[0041] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0042] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0043] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0044] Example:

[0045] Combine Figure 1 This embodiment describes a variable stiffness compliant gripping device based on the Archimedean spiral principle, comprising a DC motor 1, a drive mechanism 2, a gripper base 3, and a top gripper assembly; the top gripper assembly comprises a top left gripper arm and a top right gripper arm, the top left gripper arm and the top right gripper arm having identical structures, and the drive ends of the two grippers meshing with each other;

[0046] The DC motor 1 drives the top jaw assembly located on the jaw base 3 to open or close through the drive mechanism 2;

[0047] The driving mechanism 2 includes a driving plate 2-1, a transmission rocker 2-5, and two lower swing arms 2-2, two spring mounting brackets 2-3, two springs 2-4, a slider 2-7 and two upper swing arms 2-6 arranged inside the driving plate 2-1;

[0048] The two lower swing arms 2-2, the two spring mounting brackets 2-3 and the two springs 2-4 are all arranged on the surface of the driving disk 2-1. After each upper swing arm 2-6 is buckled with a lower swing arm 2-2, each is connected to a spring mounting bracket 2-3 via a spring 2-4 to form a swing arm assembly. The lower swing arms 2-2 in the two swing arm assemblies are always kept parallel and the installation directions of the two are opposite. The head ends of the two lower swing arms 2-2 are rotatably connected to the surface of the driving disk 2-1, and the two spring mounting brackets 2-3 are fixed to the surface of the driving disk 2-1.

[0049] The transmission rocker 2-5 is a T-bar, and a slider 2-7 is connected to each end of the horizontal bar of the T-bar. Each slider 2-7 slides in the groove in the upper swing arm 2-6 and the lower swing arm 2-2. The vertical bar of the T-bar extends out of the drive disk 2-1 and is fixedly connected to the top left clamping claw arm.

[0050] Specifically, if Figure 4 This embodiment is applicable to the end of a 3D-freedom robot arm, and is fixedly connected to the 3D-freedom robot arm through an assembly bracket 4 to complete flexible grasping work.

[0051] In addition, in order to ensure that the compliant grasping device can work normally, there is theoretically serial port power supply and communication between it and the freedom robot arm.

[0052] The following further introduces the structural composition of the top left gripper arm and the top right gripper arm:

[0053] The top left gripper arm and the top right gripper arm each include a gripper upper arm 5, a gripper middle arm 6 and a gripper lower arm 7;

[0054] The clamping arm 5 of the top left clamping arm and the clamping arm 5 of the top right clamping arm are both arranged on the upper surface of the clamping base 3, and one end of the two clamping arms 5 serves as the driving end of the corresponding top left clamping arm and top right clamping arm for engagement;

[0055] The vertical rod of the T-shaped rod extends out of the drive disk 2-1 and is fixedly connected to the clamping arm 5 of the left clamping arm of the top layer. The other end of each clamping arm 5 is fixedly connected to one end of a clamping small arm 7. One end of the two clamping middle arms 6 is symmetrically arranged on the upper surface of the clamping base 3 along the meshing line 10, and the two clamping middle arms 6 are both rotatably connected to the clamping base 3; the other end of each clamping middle arm 6 is rotatably connected to the middle part of each clamping small arm 7.

[0056] Specifically, Figure 1 A single-layer gripper is used to grasp an object, that is, a top-layer left gripper arm and a top-layer right gripper arm are used; for the gripper middle arm 6, its configuration significance is as follows:

[0057] 1. Adding a middle arm to form a triangular connecting rod swing mechanism with the upper arm and lower arm increases the stability of the gripper.

[0058] 2. Adding a stress point in the middle of the forearm reduces the bending moment of the forearm and avoids damage to the forearm.

[0059] 3. The length of the middle arm can be adjusted manually. By adjusting its length, the force arm can be changed, thereby changing the output torque at the end of the gripper.

[0060] The best solution can be flexibly selected according to different task requirements.

[0061] The following further introduces the connection relationship of the double-layer gripper:

[0062] The device also includes a drive shaft and a bottom jaw assembly;

[0063] The bottom clamp assembly includes a bottom left clamp arm and a bottom right clamp arm; the bottom left clamp arm and the bottom right clamp arm have the same structure as the top left clamp arm or the top right clamp arm; the bottom left clamp arm and the top left clamp arm are arranged opposite to each other, and the bottom right clamp arm and the top right clamp arm are arranged opposite to each other;

[0064] The bottom left gripper arm and the bottom right gripper arm are both arranged on the lower surface of the gripper base 3, the bottom left gripper arm and the bottom right gripper arm are meshed, the bottom left gripper arm and the top left gripper arm are connected by a transmission shaft, and the two move synchronously, the bottom right gripper arm and the top right gripper arm are connected by a transmission shaft, and the two move synchronously.

[0065] Specifically, the flexible gripping device is suitable for gripping soil clods. The top gripping jaw assembly is used to grip objects, and the bottom gripping jaw assembly is provided to make the gripping force more suitable.

[0066] The following further introduces the preferred structure of the double-layer gripper:

[0067] The device also includes a No. 1 connecting rod 8, a No. 2 connecting rod and a No. 3 connecting rod 9;

[0068] The top left gripper arm, the top right gripper arm, the bottom left gripper arm and the bottom right gripper arm all include a gripper upper arm 5, a gripper middle arm 6 and a gripper lower arm 7;

[0069] The clamping arm 5 of the top left clamping arm and the clamping arm 5 of the top right clamping arm are both arranged on the upper surface of the clamping base 3, and one end of the two clamping arms 5 are meshed. The clamping arm 5 of the bottom left clamping arm and the clamping arm 5 of the bottom right clamping arm are both arranged on the lower surface of the clamping base 3, and one end of the two clamping arms 5 are meshed.

[0070] The gripper arm 5 of the bottom right gripper arm and the gripper arm 5 of the top right gripper arm are connected via a transmission shaft, and the bottom right gripper arm and the top right gripper arm are connected via a transmission shaft;

[0071] The vertical rod of the T-shaped rod extends out of the drive disk 2-1 and is fixedly connected to the clamping arm 5 of the left clamping arm of the top layer. The other end of each clamping arm 5 is fixedly connected to one end of a clamping small arm 7. The two clamping small arms 7 on the same side are connected by a No. 1 connecting rod 8. The two No. 2 connecting rods pass through the clamping base 3, and the two No. 2 connecting rods are symmetrically arranged along the meshing line 10. The two ends of the two No. 2 connecting rods are respectively exposed to the upper and lower surfaces of the clamping base 3. One end of the two clamping middle arms 6 on the same side is respectively mounted on the two ends of a No. 2 connecting rod on the same side, and the clamping middle arm 6 is rotatably connected to the No. 2 connecting rod. Each No. 3 connecting rod 9 passes through the middle of the two clamping small arms 7 on the same side, and the two ends of each No. 3 connecting rod 9 expose the surface of the two clamping small arms 7. The other ends of the two clamping middle arms 6 on the same side are respectively mounted on the two ends of the No. 3 connecting rod 9 on the same side, and the clamping middle arm 6 is rotatably connected to the No. 3 connecting rod 9.

[0072] Specifically, in the initial state, the DC motor 1 is fixedly connected to the driving mechanism 2, and the driving mechanism 2 is fixedly connected to the clamping arm 5 via its transmission rocker 2-5 and the central axis of the disc, forming the power source of the entire grasping device.

[0073] In the initial state, in the driving mechanism 2, the spring mounting frame 2-3 is fixedly connected to the driving disc 2-1, and the spring 2-4 hook has one end mounted on the lower arm 2-2 and the other end mounted on the spring mounting frame 2-3. Figure 3 As shown, slider 2-7 comprises a lower slider 2-7-1 and an upper slider 2-7-3. The lower slider 2-7-1 and the upper slider 2-7-3 are connected via a pin 2-7-2 and a drive rocker 2-5, allowing them to rotate about the pin 2-7-2. The lower slider 2-7-1 is positioned within a groove in the lower swing arm 2-2, while the upper slider 2-7-3 is positioned within a groove in the upper swing arm 2-6. Both sliders can slide within their grooves. The upper swing arm 2-6 is connected to the lower swing arm via two bolts at the head and tail, allowing it to swing along with the lower swing arm 2-2 about the bolts.

[0074] Symmetrically, the lower swing arm 2-2 is connected to the drive disc 2-1 by bolts, the spring mounting frame 2-3 is fixedly connected to the drive disc 17, and a gasket is added between them to reduce the friction between the swing arm and the drive disc when the swing arm rotates.

[0075] The following is a further introduction to the structural composition of the gripper's middle arm:

[0076] The middle arms 6 of the clamping jaws are all telescopic structures with adjustable length.

[0077] Specifically, if Figure 8As shown, each clamping jaw middle arm 6 includes an outer sleeve 6-1 and an inner sleeve 6-2; the outer sleeve 6-1 is hollow inside and is inserted into the outer sleeve 26. The length of the clamping jaw middle arm 6 can be adjusted through the outer sleeve 6-1 and the inner sleeve 6-2, and the outer sleeve 26 and the inner sleeve 27 are fixed by bolts to achieve the effect of changing their length.

[0078] The control of the linear motor is described below: the device also includes a controller and a serial communication module;

[0079] The controller is used to control the operation of the DC motor 1 through the serial communication module.

[0080] The structure further included in this device is introduced below:

[0081] The device also includes 2 spacers;

[0082] A gasket is provided between the head ends of the two lower swing arms 2-2 and the driving disc 2-1.

[0083] Specifically, the lower swing arm 2-2 is connected to the drive plate 2-1 by bolts, and a gasket is added therebetween to reduce the friction between the swing arm and the drive plate when the swing arm rotates.

[0084] Working principle:

[0085] Step 1: Motor drive: The controller sends a command and transmits it to DC motor 1 via serial communication, and DC motor 1 starts.

[0086] Step 2: The driving disc rotates. Since the DC motor 1 is fixedly connected to the driving disc 2, the driving disc 2 rotates around the central axis under the action of the DC motor 1.

[0087] Step 3: Swinging of the swing arms. Since there is a load at the end of the transmission rocker 2-5, when the driving disc 2 moves, the two lower swing arms 2-2 and the two upper swing arms 2-6 will respectively rotate relative to the driving disc 2 around the fixing bolts.

[0088] Step 4: Spring extension: Driven by the swing arm, the two springs 2-7-1 extend, and the system stiffness changes accordingly.

[0089] Step 5: Sliding blocks slide. As the swing arm swings, the two lower sliding blocks 2-7-2 slide relative to each other in the grooves of the two lower swing arms 2-2. Similarly, the two upper sliding blocks 2-7-3 slide relative to each other in the grooves of the two upper swing arms 2-6.

[0090] Step 6: Rocker rotation. Due to the symmetrical distribution of the entire system, under the action of the two pins 2-7-2, the two upper sliders 2-7-3 and the two lower sliders 2-7-1 will drive the transmission rocker 2-5 to rotate around the central axis.

[0091] Step 7: Rotation of the clamping arm in the left clamping arm of the top layer. Since the transmission rocker 2-5 is coaxially fixedly connected to the clamping arm in the left clamping arm of the top layer, the clamping arm of the left clamping arm of the top layer will rotate around the bolt on the clamping base 3 along with the transmission rocker 2-5.

[0092] Step 8: The gripper arm in the left gripper arm of the bottom layer rotates. The gripper arm in the left gripper arm of the bottom layer rotates synchronously with the gripper arm in the left gripper arm of the top layer through the transmission shaft.

[0093] Step 9: The upper jaw arm in the right gripper arm of the top layer and the upper jaw arm in the right gripper arm of the bottom layer rotate. The upper jaw arm in the right gripper arm of the top layer rotates around the bolt on the gripper base 3 driven by the upper jaw arm in the left gripper arm of the top layer via a gear transmission. The upper jaw arm in the right gripper arm of the bottom layer rotates around the bolt on the gripper base 3 driven by the upper jaw arm in the left gripper arm of the bottom layer via a gear transmission.

[0094] Step 10: The middle arm of the clamp rotates. The upper arm of the clamp drives the middle arm of the clamp to rotate around the bolts fixed on the clamp base 3 respectively through the transmission of the lower arm of the clamp.

[0095] Step 11: The gripper arm performs a planar motion. Driven by the upper and middle arms, the gripper arm performs a planar motion to tighten the gripper.

[0096] Step 12: Grasp the target. The four gripper arms retract separately to achieve a smooth grasp of the target object.

[0097] Experimental verification:

[0098] In order to ensure that the clamping mechanism can achieve variable stiffness function during the clamping process and complete the flexible clamping task, the dynamic modeling analysis of the entire mechanism is carried out to explore the relationship between the clamping torque and the rotation angle of the driving mechanism, and analyze the influence of different spring selections on the clamping torque.

[0099] To investigate whether variable stiffness can be achieved during the mechanism's motion, we performed modeling calculations in simulation software. Conventional motors typically output at a constant speed, so a constant speed must be assigned to the drive disc 2-1 in the simulation software.

[0100] Through simulation, we plotted the relationship between the output torque of the transmission rocker 2-5 and time. Figure 7 As shown. Figure 7 It can be seen that under the condition of constant speed input, the output torque of the driving mechanism 2 generally shows a downward trend, and the process can be roughly divided into three parts: the output torque first experiences a large decrease, then the change amplitude tends to be gentle, and finally the decrease speed increases slightly.

[0101] In order to verify the compliant grasping function of the mechanism, we observed the output torque at the end of the gripper at different rotation angles.

[0102] The simulation calculation is carried out when the spring stiffness is 1N / mm, and the calculation results are shown in Table 1.

[0103] Table 1 Analysis of output torque at the end of the gripper

[0104]

[0105] The simulation results show that the output torque of the gripper changes during the movement of the drive mechanism, which can meet the needs of smooth grasping.

[0106] To ensure suitability for different grasping tasks, the relationship between spring selection and output torque needs to be analyzed. Different springs can be selected to meet various task requirements. The corresponding gripper output torques for different spring selections are shown in Table 2.

[0107] Table 2 Spring selection analysis

[0108]

[0109] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the invention. It should be understood that many modifications may be made to the illustrative embodiments, and that other arrangements may be devised, without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in ways other than those described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be employed in conjunction with other described embodiments.

Claims

1. A variable stiffness compliant gripping device based on the Archimedean spiral principle, characterized in that: The device comprises a DC motor (1), a drive mechanism (2), a clamping jaw base (3) and a top clamping jaw assembly; the top clamping jaw assembly comprises a top left clamping jaw arm and a top right clamping jaw arm, the top left clamping jaw arm and the top right clamping jaw arm have the same structure, and the driving ends of the two are engaged; The DC motor (1) drives the top clamping jaw assembly located on the clamping jaw base (3) to open or close through the driving mechanism (2); The driving mechanism (2) includes a driving disk (2-1), a transmission rocker (2-5), and two lower swing arms (2-2), two spring mounting frames (2-3), two springs (2-4), a slider (2-7), and two upper swing arms (2-6) arranged inside the driving disk (2-1); Two lower swing arms (2-2), two spring mounting frames (2-3) and two springs (2-4) are all arranged on the surface of the driving disk (2-1); each upper swing arm (2-6) is buckled with a lower swing arm (2-2) to form an integrated component; each integrated component is connected to a spring mounting frame (2-3) via a spring (2-4); and the upper swing arm (2-6), the lower swing arm (2-2), the spring (2-4) and the spring mounting frame (2-3) together form a swing arm assembly; the lower swing arms (2-2) in the two swing arm assemblies always remain parallel, and the two are installed in opposite directions; the head ends of the two lower swing arms (2-2) away from the springs (2-4) are rotatably connected to the surface of the driving disk (2-1); and the two spring mounting frames (2-3) are both fixed on the surface of the driving disk (2-1); The transmission rocker (2-5) is a T-shaped rod, and a slider (2-7) is connected to each end of the horizontal rod of the T-shaped rod. Each slider (2-7) slides in a groove in the upper swing arm (2-6) and the lower swing arm (2-2). The vertical rod of the T-shaped rod extends out of the driving disk (2-1) and is fixedly connected to the top left clamping claw arm.

2. The variable stiffness compliant grasping device based on the Archimedean spiral principle according to claim 1, characterized in that: The top left clamping arm and the top right clamping arm each include a clamping upper arm (5), a clamping middle arm (6) and a clamping lower arm (7); The clamping arm (5) of the top left clamping arm and the clamping arm (5) of the top right clamping arm are both arranged on the upper surface of the clamping base (3), and one end of the two clamping arms (5) serves as the driving end of the corresponding top left clamping arm and top right clamping arm for engagement; The vertical rod of the T-shaped rod extends out of the driving disk (2-1) and is fixedly connected to the clamping arm (5) of the clamping arm on the left side of the top layer. The other end of each clamping arm (5) is fixedly connected to one end of a clamping arm (7). One end of the two clamping middle arms (6) is symmetrically arranged on the upper surface of the clamping base (3) along the meshing line (10), and the two clamping middle arms (6) are both rotatably connected to the clamping base (3); the other end of each clamping middle arm (6) is rotatably connected to the middle of each clamping arm (7).

3. The variable stiffness compliant grasping device based on the Archimedean spiral principle according to claim 1, characterized in that: The device also includes a drive shaft and a bottom jaw assembly; The bottom clamping jaw assembly includes a bottom left clamping jaw arm and a bottom right clamping jaw arm; The bottom left gripper arm and the bottom right gripper arm have the same structure as the top left gripper arm or the top right gripper arm; the bottom left gripper arm and the top left gripper arm are arranged opposite to each other, and the bottom right gripper arm and the top right gripper arm are arranged opposite to each other; The bottom left gripper arm and the bottom right gripper arm are both arranged on the lower surface of the gripper base (3), the bottom left gripper arm and the bottom right gripper arm are meshed, the bottom left gripper arm and the top left gripper arm are connected via a transmission shaft, and the two move synchronously, and the bottom right gripper arm and the top right gripper arm are connected via a transmission shaft, and the two move synchronously.

4. The variable stiffness compliant grasping device based on the Archimedean spiral principle according to claim 3, characterized in that: The device further comprises a first connecting rod (8), a second connecting rod and a third connecting rod (9); The top left gripper arm, the top right gripper arm, the bottom left gripper arm and the bottom right gripper arm all include a gripper upper arm (5), a gripper middle arm (6) and a gripper lower arm (7); The clamping arm (5) of the top left clamping arm and the clamping arm (5) of the top right clamping arm are both arranged on the upper surface of the clamping base (3), and one end of the two clamping arms (5) are meshed. The clamping arm (5) of the bottom left clamping arm and the clamping arm (5) of the bottom right clamping arm are both arranged on the lower surface of the clamping base (3), and one end of the two clamping arms (5) are meshed. The gripper arm (5) of the bottom right gripper arm and the gripper arm (5) of the top right gripper arm are connected via a transmission shaft, and the bottom right gripper arm and the top right gripper arm are connected via a transmission shaft; The vertical rod of the T-shaped rod extends out of the driving disk (2-1) and is fixedly connected to the clamping arm (5) of the clamping arm on the left side of the top layer. The other end of each clamping arm (5) is fixedly connected to one end of a clamping arm (7). The two clamping arms (7) on the same side are connected by a No. 1 connecting rod (8). The two No. 2 connecting rods pass through the clamping base (3), and the two No. 2 connecting rods are symmetrically arranged along the meshing line (10). The two ends of the two No. 2 connecting rods are exposed from the upper and lower surfaces of the clamping base (3). One end of the two clamping jaws (6) is respectively mounted on the two ends of a No. 2 connecting rod on the same side, and the clamping jaws (6) is rotatably connected to the No. 2 connecting rod. Each No. 3 connecting rod (9) passes through the middle of the two clamping jaws (7) on the same side, and the two ends of each No. 3 connecting rod (9) are exposed on the surface of the two clamping jaws (7). The other ends of the two clamping jaws (6) on the same side are respectively mounted on the two ends of the No. 3 connecting rod (9) on the same side, and the clamping jaws (6) are rotatably connected to the No. 3 connecting rod (9).

5. The variable stiffness compliant grasping device based on the Archimedean spiral principle according to claim 2 or 4, characterized in that: The middle arms (6) of the clamping jaws are all telescopic structures with adjustable lengths.

6. The variable stiffness compliant grasping device based on the Archimedean spiral principle according to claim 1, characterized in that: The device also includes a controller and a serial communication module; The controller is used to control the operation of the DC motor (1) through the serial communication module.

7. The variable stiffness compliant grasping device based on the Archimedean spiral principle according to claim 1, characterized in that: The device also includes 2 spacers; A gasket is respectively provided between the head ends of the two lower swing arms (2-2) and the driving disc (2-1).

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