Shape memory alloy driven multi-movement modality micro soft-bodied robot

Abstract

The application provides a shape memory alloy driven multi-motion mode micro soft robot, which comprises an elastic framework, an SMA driver and a mechanism bottom passive friction device; the SMA driver is fixed on the front and back surfaces of the elastic framework; the mechanism bottom passive friction device is fixed on the end of the elastic framework; the elastic framework is used for providing pre-deformation of the SMA driver at room temperature and restoring the SMA driver to the initial pre-deformation mode by using elastic potential energy; the SMA driver is used for axial compression under external electric field heating, the generated tension causes the unidirectional bending deformation of the elastic framework fixedly connected therewith, so as to generate a propelling force to drive the robot to realize a preset motion mode; and the mechanism bottom passive friction device is used for realizing a unidirectional friction force structure and realizing the directional crawling of the robot. The soft robot system of the application has high motion flexibility and adaptability and can perform diversified motion and exploration in a complex environment.

Description

Technical Field

[0001] The present invention relates to the technical field of soft robots, and in particular to a multi-motion modality micro soft robot driven by a shape memory alloy. Background Art

[0002] Robots constructed from rigid materials have made significant progress over the past few decades. Designed for specific tasks or groups of tasks, these robots exhibit efficient task specificity and exceptional precision. Rigid materials impart remarkable precision to robots, enabling accurate motion and control during operation. However, the inflexibility of rigid robots limits their adaptability to diverse tasks and environments, particularly their lack of safety and flexibility in dynamic environments.

[0003] To meet diverse needs, scientists have begun to draw inspiration from invertebrates and plants to study continuum robots and soft robots. Made of flexible materials similar to biological tissue, soft robots are inherently soft and compliant due to their design and manufacturing processes, enabling them to perform a variety of tasks that rigid robots are unable to accomplish, such as deep-sea exploration, diving operations, and complex surface movements.

[0004] The deformability of soft robots makes them well-suited for navigating complex, unstructured environments. Researchers have developed a variety of efficient and reliable soft robot configurations and designs for tasks in diverse environments, including oceans, pipelines, and vertical surfaces. While these soft robots exhibit exceptional efficiency, most are only applicable to specific environments, severely limiting their capabilities and range across diverse motion environments.

[0005] In the real world, multi-animals typically have multiple modes of motion to adapt to different environments. Based on biomimetic thinking, soft robots achieve multi-modal motion through clever mechanical structure and drive design, mimicking the movement of multi-animals to adapt to different environments. Currently, there are some representative works at home and abroad, such as:

[0006] Salamander-like amphibious soft robot: This soft robot can swim like an eel in water and crawl on land. It generates wave-like motion by oscillating its body, propulsing itself through interaction with the environment. The robot's speed is positively correlated with the frequency of its oscillations, and its direction and posture can be adjusted by varying the curvature of its body.

[0007] Jumping origami soft robot: This soft robot uses shape memory alloy as muscles, and can jump by adjusting its shape and exerting force, adapting to narrow and complex spaces.

[0008] Small insect-like amphibious robot: this small insect-like robot can fly, walk, and adapt to ground, air and water environments.

[0009] Patent document CN110076749A (application number: CN201910503103.2) discloses a jellyfish-like magnetic control micro-soft robot, which comprises a head and five movable arms arranged in a radial manner on the circumference of the head in the same plane; wherein the movable arm comprises an upper arm, a forearm and a hand; the head, the upper arm, the forearm and the hand are connected in sequence through elastic tendons; the head, the upper arm, the forearm and the hand are all rigid parts with different magnetic field directions, so that the five movable arms can move in multiple degrees of freedom under the action of an external magnetic field and can be bent and held together into a dodecahedron under the action of an external magnetic field.

[0010] Although the above research partially solves the application problem of soft robots in complex environments, there are still many challenges, such as coping with uneven roads and low obstacles. Research shows that the rolling ability of soft robots may have potential in this regard, but the current research is relatively limited. SUMMARY

[0011] In view of the defects in the prior art, the purpose of the present application is to provide a shape memory alloy driven multi-motion mode micro-soft robot.

[0012] The shape memory alloy driven multi-motion mode micro-soft robot provided by the present application comprises an elastic skeleton, an SMA driver and a mechanism bottom passive friction device;

[0013] The SMA driver is fixed on the front and back surfaces of the elastic skeleton;

[0014] The mechanism bottom passive friction device is fixed at the end of the elastic skeleton;

[0015] The elastic skeleton is the main body of the robot mechanism, which is used to provide pre-deformation of the SMA driver at room temperature, and to restore the relaxed state SMA driver to the initial pre-deformation mode by using elastic potential energy;

[0016] The SMA driver is used to be axially compressed under external electric field heating, and the generated tensile force causes the elastic skeleton fixed thereto to bend in one direction, thereby generating a propulsion force to drive the robot to realize the preset motion mode;

[0017] The mechanism bottom passive friction device is used to realize a one-way friction force structure to realize the directional crawling of the robot and enable the basic motion ability of the robot.

[0018] Preferably, the SMA driver is an orthodontic tension spring.

[0019] Preferably, the auxiliary materials include: power cord and thermal insulation tape;

[0020] The power line is connected to the external power supply and the SMA driver to provide the SMA driver with a working current;

[0021] The heat-insulating adhesive tape is adhered to the front and back surfaces of the elastic frame.

[0022] Preferably, the elastic skeleton selection requirements include two factors: one is to provide sufficient support force to achieve the desired pre-deformation degree of the SMA actuator; the other is to provide sufficiently large elastic potential energy as a restoring force to ensure that the SMA actuator switches between the extension and contraction states.

[0023] Preferably, the SMA actuator selection requirements include: considering the responsiveness to temperature, deformation rate and maximum load; considering that when the robot performs crawling and jumping movements, the SMA actuator needs to generate a sufficiently large pulling force so that the bending degree of the elastic skeleton can meet the task requirements.

[0024] Preferably, the selection of the power cord includes two factors: one is to ensure that the SMA driver can stably provide a sufficiently large working current; the other is to use a lightweight wire material so as not to affect the movement of the robot.

[0025] Preferably, the thermal insulation tape uses a double layer of thermal insulation tape as the thermal insulation layer, with the glue surfaces adhered to each other and the non-glue surfaces facing outwards.

[0026] Preferably, the assembly process is:

[0027] Step S1: integrating the selected materials;

[0028] Step S2: Based on energy conservation, the robot motion is modeled and analyzed;

[0029] Step S3: Design a bistable structure to expand and realize the jumping function of the mechanism;

[0030] Step S4: According to the driving mechanism of the SMA actuator, a control method of connecting a switch circuit in series with the SMA actuator is adopted to effectively control the temperature of the SMA actuator.

[0031] Preferably, the step S2 includes:

[0032] Assuming the initial bending angle of the elastic skeleton is 0, the strain energy stored in the plate due to bending relative to θ is:

[0033]

[0034] The tensile strain energy in the SMA actuator is:

[0035]

[0036] Where, under different bending angles θ, when θ<0, the elastic skeleton bends downward; when θ>0, the elastic skeleton bends upward. In each case, the first term corresponds to the strain energy of the SMA actuator placed on the lower side of the elastic skeleton; the second term corresponds to the strain energy of the SMA actuator on the upper side of the elastic skeleton. Assuming that the deformation of the SMA actuator is linearly related to the temperature, L max , L0 represent the stretched length and initial length of the SMA actuator, respectively; k1 and k2 represent the SMA spring stiffness;

[0037] The total potential energy of the system during bending is: U t =U SMA +U bend .

[0038] Preferably, step S3 includes: designing the initial state of the mechanism to be a straight line, combining energy distribution and tensile potential energy to make the total energy in the mechanism symmetrically distributed, heating the SMA actuators on both sides, and increasing the stiffness k of the SMA actuators, so that the total energy of the system has two symmetrical local minimum points on the left and right sides, that is, two stable states. In this way, the SMA actuators store / release energy during the bending process, generate transient dynamics after the energy peak, and drive the robot to jump and climb over as a whole.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] The present invention provides a shape memory alloy-driven multi-motion mode micro soft robot. In addition to traditional crawling motion, the bistable structure adopted by the robot additionally gives it jumping ability, which can climb over obstacles and improve its applicability for exploration tasks in rugged obstacle environments. The soft robot system of the present invention has a high degree of motion flexibility and adaptability, and can perform diverse motions and explorations in complex environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0042] Figure 1 Schematic diagram of the soft robot system;

[0043] Figure 2 Schematic diagram of the crawling motion of the soft robot;

[0044] Figure 3 Schematic diagram of the bending state;

[0045] Figure 4 This is the system energy distribution diagram. DETAILED DESCRIPTION

[0046] The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several changes and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0047] Example

[0048] The present invention provides a shape memory alloy driven multi-motion mode micro soft robot, comprising an elastic skeleton, an SMA driver and a passive friction device at the bottom of the mechanism;

[0049] The SMA actuator is used to axially compress under external electric field heating. The resulting tension causes the elastic skeleton connected to it to unidirectionally bend and deform, thereby generating sufficient propulsion force to drive the robot to achieve a specific motion mode. Based on the results of domestic market research, an economical orthodontic tension spring was selected as the actuator.

[0050] The elastic skeleton serves as the main body of the robot mechanism, and is used to provide pre-deformation of the SMA spring at room temperature. It also uses elastic potential energy to restore the SMA spring in a relaxed state (non-working state) to its initial pre-deformed shape. Combining the SMA spring selection results and the tension generated at its maximum deformation (assuming the bending angle at this time is ), the elastic skeleton selection and geometric parameters are determined by analyzing and testing the support force and elastic potential energy provided by raw materials of different models and geometric dimensions.

[0051] The passive friction device at the bottom of the mechanism is used to realize a unidirectional friction structure, achieve directional crawling of the robot, and enable the basic movement ability of the robot;

[0052] The shape memory alloy driven multi-motion mode micro soft robot provided by the present invention also includes auxiliary materials, power cord and thermal insulation tape;

[0053] The power cord is connected to an external power source to provide working current for the SMA spring. The current carrying capacity and diameter of the power cord are determined based on the selected SMA driver parameters and the principle of not affecting the movement of the robot.

[0054] The thermal insulation tape is placed between the power cord and the elastic frame as an insulation layer, which can protect the elastic frame to a certain extent, preventing the internal elastic frame material from melting when the temperature is too high or the heating time is too long when the power is turned on, damaging the mechanism and causing movement failure; in order to avoid the adhesion of the thermal insulation tape causing damping during the bending process of the elastic frame, ensure the SMA driving effect, and at the same time avoid direct contact between the power cord and the elastic frame to cause damage to the mechanism, a double-layer thermal insulation tape (the glue sides are glued to each other, and the non-glue sides face outwards) is used as the insulation layer.

[0055] Integration of the above selected materials:

[0056] The elastic skeleton raw materials are laser cut to obtain the elastic skeletons of each leg mechanism of the bipedal robot. Double layers of thermal insulation tape are adhered to the front and back sides as a thermal insulation layer, and SMA springs are fixed on the front and back sides respectively. The specific value of the distance between the two fixed end points of the spring is adjusted according to the design requirements to achieve the required performance.

[0057] The constructed mechanism is modeled and analyzed based on the energy conservation method. The total energy of the system is mainly composed of two main components: the deformation potential energy of the elastic skeleton (bending potential energy) and the potential energy of the tensile spring (tensile potential energy). These two components are related to the initial shape of the elastic skeleton and the initial length and stiffness of the spring, respectively. Both bending and tensile energy can be approximated using functions related to the bending angle θ, such as Figure 3 shown.

[0058] Assuming the initial shape of the elastic skeleton is a bending angle of 0, the strain energy stored in the plate due to bending about θ is:

[0059]

[0060] The tensile strain energy in an SMA spring is:

[0061]

[0062] In the above formula, when θ < 0, the elastic frame bends downward; when θ > 0, the elastic frame bends upward. The first term in each formula corresponds to the strain energy of the SMA spring placed on the bottom side of the elastic frame; the second term corresponds to the strain energy of the SMA spring placed on the top side of the elastic frame. It should be noted that to simplify the calculation process, the SMA deformation is assumed to be linearly related to temperature. max L0 and L1 represent the stretched and initial lengths of the SMA spring, respectively; k1 and k2 represent the stiffness of the SMA spring. Therefore, the total potential energy of the system during bending can be calculated as:

[0063] U t =U SMA +U bend

[0064] For the prototype, a bistable structure was designed based on the overall energy analysis of the system, and the jumping function of the prototype system was expanded: the initial state of the design mechanism is a straight line (the bending angle of each leg is 0 in the initial state). In this case, the bending potential energy is a parabola with a minimum value at the bending angle of 0. Combining the energy distribution and the stretching potential energy, the total energy in the mechanism can be distributed symmetrically. See the energy distribution diagram of the system for details. Figure 4 .

[0065] The total energy distribution in this structure reaches a minimum at a bending angle of 0, representing a stable state. However, heating the SMA springs on both sides increases the spring stiffness k, causing the system's total energy to reach two symmetrical local minima on the left and right sides, creating two stable states. This allows the drive module to store and release energy during bending, generating transient dynamics after the energy peak, driving the robot to jump and climb.

[0066] Based on the driving mechanism of SMA springs, a control scheme in which a switching circuit is connected in series with the SMA spring is employed to effectively control the SMA spring temperature. Given a fixed resistance, the spring's heating power is proportional to the square of the current flowing through it. Therefore, the control circuit must be able to independently power each SMA spring on and off, and when powered on, control the current flowing through the spring to control the heating rate. After researching relevant literature, this study decided to employ a control scheme in which a universal current controller is connected in series with the SMA spring. When the load voltage is sufficiently high and does not exceed the maximum allowable voltage of the current controller, the current controller operates in the constant current region, directly determining the current flowing through the SMA spring and thus achieving temperature control.

[0067] This project ultimately decided to utilize a multi-channel current control board and a universal master development board for control, with a high-power DC power supply serving as the load power source. The universal master development board's digital outputs can generate an analog potential output of approximately 0-5V. In operation, up to eight SMA springs can be connected in series to each current controller circuit. The corresponding digital output pins on the universal master development board are connected to the control pins of the current controller circuit. The positive and negative terminals of the DC power supply driving the SMA springs are connected to the load power supply terminals of the current controller circuit to complete the controller connection. During control, the control code defines the digital output level for each channel (ranging from 0-255) to control the power on and off of each SMA spring and the current level.

[0068] like Figure 1 , showing a schematic diagram of a multi-motion mode soft robot system. The system includes a shape memory alloy (SMA) drive module, a foot directional friction structure, a control circuit, and a motion mode switching module. The SMA drive module achieves phase change of the SMA by heating it with electricity, thereby realizing the robot's movement. The foot directional friction structure can adjust the friction force distribution according to the robot's movement direction and needs, achieving directional movement. The control circuit achieves switching between multiple motion modes through a carefully designed SMA power-on time sequence.

[0069] like Figure 2, showing a schematic diagram of a soft robotic system performing crawling motion. Since the elastic skeleton does not need to cross the equilibrium point in a bistable state during crawling and only needs to bend back and forth on one side, the time difference Δt between the start of energization of the SMA springs on both sides can be appropriately shortened, allowing the robot to achieve alternating bending of its front and rear legs, thereby achieving crawling motion.

[0070] In the description of this application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0071] Those skilled in the art will appreciate that, in addition to implementing the system, device, and various modules provided by the present invention in purely computer-readable program code, it is entirely possible to implement the same program in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, embedded microcontrollers, and the like by logically programming the method steps. Therefore, the system, device, and various modules provided by the present invention can be considered a hardware component, and the modules included therein for implementing various programs can also be considered structures within the hardware component; the modules for implementing various functions can also be considered both software programs for implementing the method and structures within the hardware component.

[0072] The above describes specific embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. The embodiments of this application and the features in the embodiments may be combined with each other in any manner unless there is a conflict.

Claims

1. A shape memory alloy driven multi-motion mode micro soft robot, characterized in that: include: Elastic skeleton, SMA actuator and passive friction device at the bottom of the mechanism; The SMA actuator is fixed on the front and back sides of the elastic frame; The passive friction device at the bottom of the mechanism is fixed to the end of the elastic frame; The elastic skeleton is the main body of the robot mechanism, which is used to provide the SMA actuator with pre-deformation at room temperature and use elastic potential energy to restore the relaxed SMA actuator to the initial pre-deformed shape; The SMA actuator is used to axially compress under external electric field heating, and the resulting tension causes the elastic skeleton connected to it to unidirectionally bend and deform, thereby generating a propulsion force to drive the robot to achieve a preset motion mode; The passive friction device at the bottom of the mechanism is used to realize a unidirectional friction structure, thereby achieving directional crawling of the robot and giving the robot basic movement capabilities; The initial state of the designed mechanism is a straight line. Combining energy distribution and tensile potential energy, the total energy in the mechanism is distributed symmetrically. By heating the SMA actuators on both sides, the stiffness k of the SMA actuators increases, causing the total energy of the system to have two symmetrical local minimum points on the left and right sides, that is, two stable states. In this way, the SMA actuators store and release energy during the bending process, generating transient dynamics after the energy peak, driving the robot to jump and climb over as a whole.

2. The shape memory alloy driven multi-motion mode micro soft robot according to claim 1, characterized in that: The SMA actuator is an orthodontic tension spring.

3. The shape memory alloy driven multi-motion mode micro soft robot according to claim 1, characterized in that: Also included are auxiliary materials: power cord and thermal insulation tape; The power line is connected to the external power supply and the SMA driver to provide the SMA driver with a working current; The heat-insulating adhesive tape is adhered to the front and back surfaces of the elastic frame.

4. The shape memory alloy driven multi-motion mode micro soft robot according to claim 3, characterized in that: The thermal insulation tape uses a double layer of thermal insulation tape as the thermal insulation layer, with the glue surfaces adhered to each other and the non-glue surfaces facing outwards.

5. The shape memory alloy driven multi-motion mode micro soft robot according to any one of claims 1 to 4, characterized in that: The assembly process is: Step S1: integrating the selected materials; Step S2: Based on energy conservation, the robot motion is modeled and analyzed; Step S3: Design a bistable structure to expand and realize the jumping function of the mechanism; Step S4: According to the driving mechanism of the SMA actuator, a control method of connecting a switch circuit in series with the SMA actuator is adopted to achieve effective control of the temperature of the SMA actuator.

6. The shape memory alloy driven multi-motion mode micro soft robot according to claim 5, characterized in that: The step S2 comprises: Assuming the initial bending angle of the elastic skeleton is 0, then due to the The strain energy stored in the plate due to bending is: The tensile strain energy in the SMA actuator is: Among them, the corresponding bending angle Under different conditions, when Indicates that the elastic skeleton bends downward; when represents the upward bending of the elastic skeleton; in each equation, the first term corresponds to the strain energy of the SMA actuator placed on the lower side of the elastic skeleton; the second term corresponds to the strain energy of the SMA actuator on the upper side of the elastic skeleton; assuming that the deformation of the SMA actuator is linearly related to the temperature, 、 represent the stretched length and initial length of the SMA actuator respectively; 、 represents the SMA spring stiffness; The total potential energy of the system during bending is: .

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