Wide-width reprogrammable grasping robot based on shape memory polymer bistable buckled beam

Abstract

The present invention discloses a wide-range reproducible grasping robot based on a bistable buckling beam of a shape memory polymer. The robot comprises a bistable buckling beam structure based on a shape memory polymer, a grasping finger, a hinge module, a pneumatic telescopic actuator, a pneumatic radial actuator, an inflation system, a heating system, and the like. The bistable buckling beam structure has two stable states: a release state and a grasping state. By inflating and deflating the pneumatic telescopic actuator, the bistable buckling beam structure can be rapidly switched between the two stable states. By inflating and deflating the pneumatic radial actuator, the pneumatic radial actuator undergoes elastic deformation and actively adjusts the switching threshold between the two stable states, thereby achieving continuous and reproducible programming of stable-state characteristics such as monostable / bistable. By heating the bistable buckling beam structure through a heating system, the elastic modulus of the shape memory polymer can be actively regulated, thereby achieving wide-range reproducible programming of stable-state characteristics such as peak load and energy barrier.

Description

Technical Field

[0001] The invention relates to soft robot technology, in particular to a wide-width reproducible programmable grasping robot based on a shape memory polymer bistable buckling beam. Background Art

[0002] Flexible grippers belong to the field of soft robotics. Traditional flexible grippers are made of soft materials (soft rubber) and offer advantages such as softness, adaptability, and safe human-machine interaction, making them highly feasible for grasping fragile objects. The complex and diverse mechanical properties of soft materials also enrich the design options for flexible grippers. However, current flexible grippers suffer from drawbacks such as bulky drive equipment and slow grasping speeds. Furthermore, to maintain the elastic deformation generated during grasping, flexible grippers require external energy input, which results in energy waste. These shortcomings limit the practical application of flexible grippers in industry. Summary of the Invention

[0003] The purpose of the present invention is to improve the shortcomings of traditional flexible grippers, such as slow grasping response speed, complex driving methods, difficult to adjust grasping sensitivity, and the need for uninterrupted external energy supply during the grasping process. The present invention provides a wide-width reprogrammable grasping robot based on a shape memory polymer bistable buckling beam. Utilizing the reprogrammable characteristics of the bistable buckling beam, the grasping robot's trigger force, response time, grasping mode, and other characteristics can be actively controlled. This grasping robot has the characteristics of diverse modes, fast response, strong adaptability, and low cost. It does not require additional energy input to maintain the grasping state of the flexible gripper and can be applied to the end effector of an industrial robot to achieve intelligent grasping and release of various targets.

[0004] The technical solutions adopted in the present invention are as follows:

[0005] A wide-width, reprogrammable grasping robot based on a bistable buckled beam made of shape memory polymer (SMP), comprising a buckled beam structure, a grasping finger, a hinge module, a grasping finger, a pneumatic telescopic actuator, a pneumatic radial actuator, and a heating system. The buckled beam structure is a herringbone beam system composed of three buckled beams arranged circumferentially at 120°. One end of the three buckled beams is fixedly connected to each other, and the other end is hinged to the hinge module. The buckled beam is a thin shell beam with a rectangular cross-section, machined from SMP plastic. The axis of the buckled beam is shaped as two connected circular arcs, with the tangents of the two arcs at the connection collinear. The buckled beam structure has two stable states: a release state and a grasping state. The switching threshold between the two stable states is adjusted by adjusting the negative pressure of the pneumatic radial actuator. The heating system is disposed on the surface of the bistable buckled beam structure and is used to adjust the switching threshold between the two stable states.

[0006] In the above technical solution, further, the gripping fingers are made of TPU material through 3D printing, one end of which is pasted in the middle of the buckling beam and the other end is free. The gripping fingers made of soft materials can better protect the grasped object. The geometric design of the gripping fingers also ensures that when the flexible gripper is in the grasping state, the gripping fingers have a good wrapping effect on the grasped object. One end of the pneumatic telescopic actuator is connected to the fixed plate installed in the center of the "human" shaped buckling beam structure, and the other end is installed on the fixed plate arranged on the hinge unit. The pneumatic telescopic actuator is connected to the center of the buckling beam with a three-way joint. The pneumatic telescopic actuator and the pneumatic radial actuator are made of TPU film and PLA plastic plate. The PLA plastic plate has a high elastic modulus and is convenient for 3D printing and batch processing. The TPU film is used to make the air bag, and the PLA plastic plate is pasted on it to form the Miura origami unit.

[0007] Furthermore, the hinge module includes a rotating part and a rotating shaft part, and the rotating part can rotate along the rotating shaft part; one end of the pneumatic telescopic driver is fixedly connected to the center of the bistable buckling beam structure, and the other end is connected to the rotating part of the hinge module; both ends of the pneumatic radial driver are connected to the rotating shaft part of the hinge module, and multiple pneumatic radial drivers are connected in series to form a circular ring through multiple hinge modules.

[0008] Furthermore, the switching threshold between the two stable states can be adjusted by adjusting the negative pressure state of the pneumatic radial drive. The specific method is as follows: when the pneumatic radial drive is evacuated, it undergoes radial contraction and deformation, and the bistable buckling beam structure is subjected to radial extrusion pressure, which increases the switching threshold between the two stable states; by controlling the negative pressure of the pneumatic radial drive, the grasping load and the passive grasping threshold can be repeatedly programmed and designed, and are continuously adjustable.

[0009] Furthermore, the heating system is specifically composed of an electric heating film, and a layer of electric heating film is attached to the upper and lower surfaces of the bistable buckled beam structure; the heating system is used to adjust the switching threshold between the two stable states. The specific method is: when the electric heating film is energized and heated, the temperature of the bistable buckled beam structure rises and reaches the glass transition temperature, the elastic modulus drops sharply, and the switching threshold between the two stable states drops. The steady-state characteristics of the robot can be repeatedly programmed to improve the passive grasping sensitivity, and the width is adjustable.

[0010] The flexible gripper can adopt fast and slow air drive modes and passive drive modes to achieve rapid grasping and releasing of the target object.

[0011] Rapid air drive mode: When the pneumatic telescopic actuator is inflated, the pneumatic telescopic actuator applies thrust to the hinge module, and the hinge module rotates under the push of the bending moment. The bistable buckled beam structure quickly switches from the release state to the grasping state, and the flexible gripper realizes active and rapid grasping action; when the pneumatic telescopic actuator is depressurized, the actuator applies tension to the hinge module to generate bending moment, and the hinge module rotates under the action of the bending moment, so that the bistable buckled beam structure quickly switches from the grasping state to the release state, and the three grasping fingers quickly move away from each other to realize active and rapid release action; repeating the above process can realize repeated rapid grasping and releasing actions.

[0012] Slow air drive mode: The bistable buckled beam structure is initially in the released state. At this time, the pneumatic radial actuator is inflated to stretch the bistable buckled beam structure, so that the switching threshold between the two stable states decreases. After the threshold is reduced to zero, the bistable buckled beam structure cannot be maintained in the initial released state (at this time, the bistable buckled beam structure changes from bistability to monostable, and the corresponding stable state is the grasping state), and automatically returns to the grasping state. In the process of the bistable buckled beam structure automatically returning to the grasping state, the pneumatic telescopic actuator is slowly inflated, and the grasping robot realizes an active slow grasping action; in the process of the buckled beam structure returning to the grasping state, the pneumatic telescopic actuator is slowly inflated to realize a slow grasping action; after the grasping is completed, the bistable buckled beam structure is restored to the released state through a rapid air drive mode; repeating the above process can realize repeated grasping and releasing actions.

[0013] Passive drive mode: The pneumatic radial drive is pumped to form a negative pressure, and a switching threshold between the two stable states is set; the bistable buckled beam structure is initially in the released state, at which time the object to be grasped is made to contact the center position of the bistable buckled beam structure. When the contact force exceeds the switching threshold between the two stable states, the bistable buckled beam structure spontaneously switches quickly from the released state to the grasping state, and the flexible gripper realizes a passive and rapid grasping action; after the grasping is completed, the bistable buckled beam structure is restored to the released state through air drive; repeating the above process can achieve repeated rapid grasping and releasing actions.

[0014] Furthermore, the hinge module and the pneumatic radial drive constitute an annular regulator. The annular regulator is specifically a circular structure in which three hinge modules and three pneumatic radial drives are interlaced and connected, and is connected to the bistable buckling beam structure through the hinge module; the hinge module is hollowed out and connected to the pneumatic radial drive as a whole. If the gripping load-bearing capacity needs to be increased, the pneumatic radial drive is evacuated, and the pneumatic radial drive undergoes annular contraction, causing the diameter of the annular regulator to shrink, thereby subjecting the buckling beam structure to a compressive force. After being subjected to the compressive force, the buckling beam structure increases the strength of the two stable states due to the internal stress, and the switching threshold force between the two stable states increases, thereby increasing the gripping load-bearing capacity.

[0015] Furthermore, to enhance the sensitivity of passive grasping, the heating system is powered on to heat the buckling beam, raising its temperature. When the buckling beam temperature exceeds the glass transition temperature of the shape memory polymer, its elastic modulus drops significantly. This lowers the threshold for switching between the two stable states of the bistable buckled beam structure. Consequently, during passive grasping, the triggering force required after the object contacts the buckling beam is significantly reduced, significantly enhancing the sensitivity of the passive grasping method.

[0016] Furthermore, the robot also includes a control unit, which consists of a power supply, a solenoid valve, a precision pressure regulating valve, a single-chip microcomputer, a wire pipe system, a vacuum pump, and an air pressure pump; the control unit is used to control the pneumatic telescopic drive and the pneumatic radial drive to evacuate or inflate; the wire pipe system includes an air pipe, a power cord, and a signal line; the single-chip microcomputer is connected to the solenoid valve through a signal line, and the path of the solenoid valve is switched by high and low levels; the vacuum pump and the air pressure pump are both connected to the precision pressure regulating valve through an air pipe; the precision pressure regulating valve is used to control the positive or negative pressure; the solenoid valve is connected to the precision pressure regulating valve through an air pipe, and the solenoid valve controls the airflow path to inflate or evacuate the pneumatic telescopic drive and the pneumatic radial drive.

[0017] The beneficial effects of the present invention are:

[0018] The wide-range reprogrammable grasping robot based on a bistable buckled beam of a shape memory polymer (SMP) employed in the present invention not only utilizes pneumatic drive to achieve active, rapid response grasping, but also passively switches the buckled beam structure between release and grasping states. The grasper has both active and passive rapid grasping / releasing capabilities. Furthermore, while the grasping robot maintains the grasping / releasing state, it does not require continuous energy input to maintain the grasping / releasing action. In passive grasping mode, no energy input is required to grasp the object. The grasping robot can be reprogrammed to suit specific needs, such as the weight of the grasped object. By inflating and deflating the pneumatic radial actuator, the actuator elastically deforms and actively adjusts the switching threshold between the two stable states, enabling continuous and reprogrammable steady-state properties such as monostable and bistable. By heating the bistable buckled beam structure through a heating system, the elastic modulus of the SMP can be actively controlled, enabling wide and reprogrammable steady-state properties such as peak load and energy barrier. The specific structural design of the gripping robot in this invention not only facilitates stable gripping of target objects but also facilitates mass production. Therefore, the gripping robot can be used as an end effector of industrial robots to quickly and repeatedly grasp and release various targets. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1It is a schematic diagram of the structure of a wide-range reprogrammable grasping robot based on a bistable buckling beam of shape memory polymer;

[0020] Figure 2 It is a structural diagram of a buckled beam structure;

[0021] Figure 3 It is a structural diagram of the grasping fingers;

[0022] Figure 4 (1) is a schematic structural diagram of the hinge module, Figure 4 (2) is a stereoscopic diagram of the rotating component of the hinge module, and Figure 4 (3) is a stereoscopic diagram of the rotating shaft component of the hinge module;

[0023] Figure 5 (1) is a schematic diagram of the structure of the basic Miura origami unit, Figure 5 (2) is a flattened form of the basic origami unit, Figure 5 (3) is a front view of the truncated origami unit, Figure 5 (4) is a stereoscopic view of the pneumatic telescopic actuator 4 composed of the basic origami unit, and Figure 5 (5) is a stereoscopic view of the pneumatic radial actuator 5 composed of the truncated origami unit;

[0024] Figure 6 It is a structural diagram of the heating system;

[0025] Figure 7 It is a schematic diagram of the air circuit of the pneumatic telescopic actuator and the pneumatic radial actuator;

[0026] Figure 8 is a schematic diagram of the control unit;

[0027] Among them, 1: bistable buckling beam structure; 2: gripping finger; 3: hinge module; 4: pneumatic telescopic drive; 5: pneumatic radial drive; 6: heating system. DETAILED DESCRIPTION

[0028] The solution of the present invention is further explained below with reference to the accompanying drawings.

[0029] like Figure 1 The present invention is a wide-width reprogrammable grasping robot based on a shape memory polymer bistable buckling beam. The grasping robot mainly consists of a bistable buckling beam structure 1, a grasping finger 2, a hinge module 3, a pneumatic telescopic drive 4, a pneumatic radial drive 5, a heating system 6 and a control unit.

[0030] like Figure 2The figure shows a bistable buckled beam structure 1 of the present invention. The structure is a "human" shaped beam system structure formed by three buckled beams arranged circumferentially at 120 degrees. In the structure, one end of the three buckled beams is fixedly connected to each other, and the other end is hinged to the hinge module. The buckled beam has a rectangular cross-section, and the axis shape is two connected arcs, and the tangents of the two arcs at the connection are collinear. Each buckled beam is made of shape memory polymer plastic. The bistable buckled beam structure 1 has two stable states, namely: a release state and a grasping state. A pneumatic telescopic drive 4 is provided on the three buckled beam rings of the bistable buckled beam structure 1, and a pneumatic radial drive 5 is provided between the movable ends of any two adjacent buckled beam rings. By adjusting the negative pressure state of the pneumatic radial drive 5, the switching threshold between the two stable states is adjusted. The specific method is as follows: when the pneumatic radial drive 5 is evacuated, it undergoes radial contraction and deformation, and the bistable buckling beam structure 1 is subjected to radial extrusion force, which increases the switching threshold between the two stable states; by controlling the negative pressure of the pneumatic radial drive 5, the grasping load and the passive grasping threshold can be repeatedly programmed and designed, and are continuously adjustable.

[0031] like Figure 3 This is the gripping finger 2 of the present invention. Made from TPU via 3D printing, one end of the gripping finger is attached to the middle connection of the two arc segments of the buckling beam, leaving the other end free. Made from soft materials, the gripping finger can better protect the object being grasped. The arc-shaped geometry of the gripping finger also ensures that when the flexible gripper is in the grasping state, the gripping finger effectively wraps around the object.

[0032] As shown in Figure 4 (1), the hinge module 3 of the present invention includes a rotating part and a rotating shaft part, and the rotating part can rotate along the rotating shaft part. Figure 4 (2) is a three-dimensional view of the rotating part of the hinge module, and Figure 4 (3) is a three-dimensional view of the rotating shaft part of the hinge module. The rotating shaft part is provided with a rotating shaft in the middle and two fixed plates on both sides. The fixed plates on both sides of the rotating shaft part are connected to one end of the pneumatic radial drive 5. The three pneumatic radial drives 5 are connected in series with the three hinge modules 3 in a ring shape. The interior of the hinge module 3 is hollowed out and connected to the pneumatic radial drive 5 as a whole. The mounting plate on the rotating part is connected to the pneumatic telescopic drive 4, and the other end of the pneumatic telescopic drive 4 is connected to the fixed end of the bistable buckling beam structure 1.

[0033] like Figure 6The heating system 6 of the present invention is attached to the upper and lower surfaces of the bistable buckled beam structure 1 and connected to a power source via wires. The heating system 6 can be used to adjust the switching threshold between the two stable states. Specifically, when the heating system 6 is energized, the temperature of the bistable buckled beam structure 1 rises to the glass transition temperature, at which point the elastic modulus drops sharply, lowering the switching threshold between the two stable states. This allows for reprogrammable design of the robot's steady-state characteristics, improving passive grasping sensitivity and providing a wide range of adjustment.

[0034] The curved surfaces of the pneumatic telescopic actuator 4 and the pneumatic radial actuator 5 are both in the Miura origami style, which is easy to fold and unfold. The pneumatic telescopic actuator 4 and the pneumatic radial actuator 5 are both composed of multiple origami units, and the number and design parameters of the origami units are determined by the geometric dimensions of the buckling beam. The basic origami unit is shown in Figure 5 (1), which consists of two layers of folding sheets, the protruding fold part is the mountain fold, and the concave fold part is the valley fold. The upper folding sheet consists of four sides with a length of and The lower folded piece consists of four parallelograms with side lengths of and of parallelograms, where , and in order to achieve the foldable condition of Figure 5 (2), the following conditions must be met:

[0035]

[0036] At the same time, in order to design the curved arch shape of the pneumatic radial drive 5, the following relationship must be satisfied:

[0037]

[0038] In the formula The central angle of the arch formed by a single origami unit is usually When the design is good 、 、 、 After four parameters, it can be calculated by the above formula and .

[0039] The above content briefly introduces the design process of the two actuators. Figure 5 (4) is a three-dimensional diagram of the pneumatic telescopic actuator 4 composed of basic origami units, and Figure 5 (5) is a three-dimensional diagram of the pneumatic radial actuator 5 composed of the truncated origami units of Figure 5 (3).

[0040] The two independent ways and processes for the grasping robot to achieve active grasping / releasing action in the present invention are:

[0041] Air drive mode:

[0042] (1) Active grasping action: When the pneumatic telescopic actuator 4 is inflated, it pulls the bistable buckled beam structure 1. Under the action of the pulling force, the hinge structure rotates, and the bistable buckled beam structure 1 quickly switches from the release state to the grasping state. The grasping fingers 2 quickly approach each other and wrap the grasped object;

[0043] (2) Active release action: When the pneumatic telescopic actuator 4 is depressing air, it pushes the hinge structure to rotate, driving the bistable buckling beam structure 1 to quickly switch from the grasping state to the releasing state, and the grasping fingers 2 quickly move away from each other, releasing the grasped object.

[0044] By repeating (1) and (2), the bistable grasping robot can achieve repeated and rapid grasping and releasing actions.

[0045] (3) Slow grasping action: When the bistable buckled beam structure 1 is in the grasping state, the pneumatic telescopic actuator 4 evacuates air to form a negative pressure, and the pneumatic radial actuator 5 inflates and stretches the bistable buckled beam structure 1, making it difficult to maintain the bistability of the bistable buckled beam structure 1. When the bistable buckled beam structure 1 returns to the initial release state, the pneumatic telescopic actuator 4 slowly intakes air to support the bistable buckled beam structure 1 to slowly recover, thereby achieving a slow grasping action.

[0046] Passive drive mode:

[0047] (1) Passive grasping action: When the bistable buckled beam structure 1 remains in the released state, the object to be grasped contacts the center position of the bistable buckled beam structure 1. When the contact force exceeds the switching threshold between the two stable states, the bistable buckled beam structure 1 spontaneously switches quickly from the released state to the grasping state, and the flexible gripper realizes a passive rapid grasping action.

[0048] like Figure 7 The air circuits of the three pneumatic telescopic actuators are connected to the central fixed point of the bistable buckled beam structure 1 using a T-joint. From the connection between one of the pneumatic telescopic actuators and the rotating component, an air pipe is connected to the control unit. The air circuits of the three pneumatic radial actuators are connected. The air pipe is fixed to the rotating shaft component of the hinge module and is connected to the control unit via an air pipe from one of the rotating shaft components.

[0049] like Figure 8The control unit consists of a power supply, a solenoid valve, a precision pressure regulating valve, a single-chip microcomputer, a wire pipe system, a vacuum pump, and an air pressure pump; the control unit is used to control the pneumatic telescopic drive and the pneumatic radial drive to exhaust or inflate; the wire pipe system includes an air pipe, a power cord, and a signal line; the single-chip microcomputer is connected to the solenoid valve through a signal line, and the path of the solenoid valve is switched by high and low levels; the vacuum pump and the air pressure pump are both connected to the precision pressure regulating valve through an air pipe; the precision pressure regulating valve is used to control the positive or negative pressure; the solenoid valve is connected to the precision pressure regulating valve through an air pipe, and the solenoid valve controls the airflow path to inflate or exhaust the pneumatic telescopic drive and the pneumatic radial drive.

[0050] The wide-width, reprogrammable grasping robot based on a bistable buckling beam made of a shape memory polymer (SMP) exhibits advantages such as fast response, energy conservation, a simple and reliable structure, and ease of batch processing. Therefore, the grasping robot can be used as an operator for industrial robots, quickly and repeatedly grasping and releasing various objects, demonstrating its broad application scenarios and strong development potential.

Claims

1. A wide-width reprogrammable grasping robot based on a shape memory polymer bistable buckling beam, characterized in that: It includes a bistable buckling beam structure based on shape memory polymer, a gripping finger, an annular regulator, a pneumatic telescopic drive and a heating system; the annular regulator is specifically a circular structure in which three hinge modules and three pneumatic radial drives are staggered and connected, and the hinge module is hollowed out and connected to the pneumatic radial drive; the hinge module includes a rotating part and a rotating shaft part, and the rotating part can rotate along the rotating shaft part; the bistable buckling beam structure is a "human" shaped beam system structure formed by three buckling beams arranged at 120 degrees in a circumferential direction, one end of the three buckling beams is fixed to each other, and the other end is fixedly connected to the rotating part of the corresponding hinge module; the buckling beam has a rectangular cross-section, and its axis shape is two connected arcs, and the tangents of the two arcs at the connection are collinear; the gripping finger The shape is an arc, one end of which is fixed at the middle position of the buckling beam and the other end is free; one end of the pneumatic telescopic actuator is fixedly connected to a fixed plate installed at the center of the bistable buckling beam structure, and the other end is connected to the rotating component of the hinge module; the two ends of the pneumatic radial actuator are respectively connected to the rotating shaft components of adjacent hinge modules; the bistable buckling beam structure has two stable states: a release state and a grasping state; the switching threshold between the two stable states is adjusted by adjusting the negative pressure state of the pneumatic radial actuator; the heating system is composed of an electric heating film, and a layer of electric heating film is attached to the upper and lower surfaces of the buckling beam. When the electric heating film is energized and heated, the temperature of the bistable buckling beam structure rises to the glass transition temperature, and the switching threshold between the two stable states decreases; The grasping and / or releasing of the grasping robot is realized by air-driven or passive means; Air drive mode: Fast grasping: When the pneumatic telescopic actuator is inflated, it exerts a thrust on the hinge module. The hinge module rotates under the push of the bending moment, and the bistable buckled beam structure switches from the release state to the grasping state, allowing the grasping robot to achieve active and fast grasping action. Quick release: When the pneumatic telescopic actuator is pumped, it exerts tension on the hinge module, generating a bending moment. The hinge module rotates under the action of the bending moment, causing the bistable buckled beam structure to switch from the grasping state to the releasing state, and the grasping robot achieves active quick release action; Slow grasping: The bistable buckled beam structure is initially in a released state. At this time, the pneumatic radial actuator is inflated to stretch the bistable buckled beam structure, causing the switching threshold between the two stable states to drop. After the threshold drops to zero, the bistable buckled beam structure cannot maintain its initial released state and automatically returns to the grasping state. During the process of the bistable buckled beam structure automatically returning to the grasping state, the pneumatic telescopic actuator is slowly inflated, and the grasping robot performs an active slow grasping action. Passive method: The pneumatic radial actuator is pumped to form negative pressure, setting a switching threshold between two stable states. When the buckled beam structure is in the released state, the object to be grasped is made to contact the center of the bistable buckled beam structure. When the contact force increases to the switching threshold between the two stable states, the bistable buckled beam structure spontaneously switches from the released state to the grasping state, and the grasping robot realizes the passive grasping action. The curved surfaces of the pneumatic telescopic drive and the pneumatic radial drive both adopt Miura origami style; the pneumatic telescopic drive and the pneumatic radial drive both consist of a plurality of origami units.

2. The wide-width reprogrammable grasping robot based on the shape memory polymer bistable buckling beam according to claim 1, characterized in that: A rotating shaft is provided in the middle of the rotating shaft component, and two fixing plates are provided on both sides. The fixing plates are used to fix the pneumatic radial driver. A mounting plate is also provided on the rotating component, and the mounting plate is connected to one end of the pneumatic telescopic driver.

3. The wide-width reprogrammable grasping robot based on the shape memory polymer bistable buckling beam according to claim 1, characterized in that: The switching threshold between the two stable states is adjusted by adjusting the negative pressure state of the pneumatic radial drive. The specific method is: when the pneumatic radial drive is evacuated, it undergoes radial contraction deformation, the bistable buckled beam structure is subjected to radial extrusion force, and the switching threshold between the two stable states is increased.

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