CN115946787A - Starfish-like soft robot based on 4D printing and control method thereof - Google Patents
Starfish-like soft robot based on 4D printing and control method thereof Download PDFInfo
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Abstract
The invention provides a starfish-imitating soft robot based on 4D printing and a control method thereof, belonging to the technical field of robots, wherein the starfish-imitating soft robot comprises a supporting unit and 5 wrist-foot units; the 5 wrist-foot units are connected with the supporting unit in a centrosymmetric shape; each wrist-foot unit comprises a driving element and an executing element; the material of the actuating element is a liquid crystal elastomer; the driving element is attached to the upper surface of the actuating element and is connected with an external power supply, and electric energy of the external power supply is converted into heat energy to drive the actuating element to bend and deform. The structural complexity of the robot is reduced, and the environmental adaptability of the robot is improved. The control method comprises the following steps: based on the expected track, the driving elements of the wrist-foot units are electrified through an external power supply to drive the executing elements to generate bending deformation, the voltage applied to the driving elements of the wrist-foot units is controlled by adopting a closed-loop PD type iterative learning method, and the control precision of the robot motion is improved.
Description
Technical Field
The invention relates to the field of robots, in particular to a starfish-imitating soft robot based on 4D printing and a control method thereof.
Background
In recent years, inspired by mollusks such as octopus, inchworm, and paramecium in nature and unicellular organisms, research on soft robots is receiving more and more attention, and the research is gradually becoming a hot spot in the robot field. The traditional robot is generally composed of rigid parts such as gears, hinges, motors and the like, and is known to have the characteristics of high precision and high efficiency. Compared with the traditional rigid robot, the basic structure of the soft robot is made of silica gel, hydrogel and rubber lamp elastic materials, and is generally driven by shape memory alloy, dielectric elastomer, photo-thermal electromagnetic sensitive materials and the like. The soft robot has almost infinite freedom degree in theory, so the soft robot has good deformability and flexibility and is more suitable for complex environments.
At present, the manufacturing of the soft robot mainly comprises the technologies of mould casting, deposition manufacturing, 3D printing, 4D printing compounding and the like. The 3D printing technology has been rapidly developed in recent years, and is favored in the production of various complex-structured and customized software robots by virtue of the advantages of low cost, short manufacturing period, rapid production, and the like. The 4D printing technology adds a time dimension on the basis of 3D printing, and realizes recompilation of the model body structure by means of the characteristics of intelligent materials. The object printed through 4D can be reflected to external stimulation, and technical support is provided for the integrated manufacturing of the soft robot.
The Chinese patent publication No. CN108216410A, named as a starfish-like robot, discloses a starfish-like robot, which comprises a base, wherein a plurality of arc-shaped swinging devices are arranged at the edge of the base at equal intervals, and the legs are bent by utilizing a rigid structure. However, the invention has no precise control algorithm, and the rigid structure is complex, and the sensitivity and the degree of freedom are limited when the device is bent. Chinese patent publication No. CN114274162A, entitled a starfish-like soft robot with dielectric elastomer driver and flexible feet. The soft robot comprises an upper dielectric elastomer driver and a lower silica gel elastomer sole, and the crawling of the soft robot is realized by electrically driving and controlling the bending of the dielectric elastomer. However, the invention only realizes simple bending behavior by boosting or reducing voltage, does not have an accurate control algorithm, and cannot realize accurate behavior control of the soft robot.
In summary, most of the existing crawling robots adopt rigid structures, so that the crawling robot is complex in structure and difficult to play a role in a complex environment. In addition, in the aspect of controlling the soft robot, a control algorithm depending on a model is mostly adopted, and the model of the soft robot has nonlinearity, so that the problems of difficult modeling, inaccurate model and the like exist.
Disclosure of Invention
The invention aims to provide a starfish-like soft robot based on 4D printing and a control method thereof, which can reduce the structural complexity of the robot, improve the environmental adaptability of the robot and accurately control the motion of the robot.
In order to achieve the purpose, the invention provides the following scheme:
a starfish-like soft robot based on 4D printing comprises: a support unit and 5 wrist-foot units; the 5 wrist-foot units are connected with the supporting unit in a centrosymmetric manner;
each wrist-foot unit comprises a driving element and an executing element;
the actuating element is made of a liquid crystal elastomer;
the driving element is attached to the upper surface of the execution element and is connected with an external power supply; the driving element is used for converting electric energy of an external power supply into heat energy so as to drive the actuating element to generate bending deformation.
Optionally, the supporting unit is a double-layer polyimide film.
Optionally, each wrist-foot unit further comprises a sensing element;
the sensing element is attached to the lower surface of the actuating element; the sensing element is used for detecting the bending angle of the actuating element.
Optionally, the sensing element is a bending curvature sensor.
Optionally, the driving element includes a polyimide film and a grid-shaped carbon nanotube; and the latticed carbon nano tubes are imprinted on the surface of the polyimide film.
Optionally, the shape of the supporting unit is a regular pentagon; the wrist-foot units are all rectangular;
one end of each wrist-foot unit is fixedly connected with one edge of the supporting unit respectively.
In order to achieve the above purpose, the invention also provides the following scheme:
a control method of a starfish-imitating soft body robot based on 4D printing is used for controlling the starfish-imitating soft body robot based on 4D printing, and the control method of the starfish-imitating soft body robot based on 4D printing comprises the following steps:
acquiring an expected track; the expected track comprises expected bending angles of the wrist-foot units at all times in one motion cycle;
based on the expected track, the driving element of each wrist-foot unit is electrified through an external power supply to drive the executing element to generate bending deformation, and the voltage applied to the driving element of each wrist-foot unit is controlled by adopting a closed-loop PD type iterative learning method, so that each wrist-foot unit moves according to the expected track.
Optionally, the controlling the voltage applied to the driving element of each wrist-foot unit by using the closed-loop PD type iterative learning method specifically includes:
aiming at the kth iteration, acquiring a control quantity in the kth iteration process; the control quantity is the voltage applied to the driving element of each wrist-foot unit; 0 and n & lt k;
for any wrist-foot unit, detecting the actual bending angle of an actuating element through a sensing element of the wrist-foot unit;
determining the bending angle error of the wrist-foot unit in the kth iteration process according to the actual bending angle and the expected bending angle of the wrist-foot unit;
and judging whether the bending angle error of each wrist-foot unit in the kth iteration process is smaller than a set threshold value, if so, stopping iteration control, and otherwise, determining the control quantity in the (k + 1) th iteration process according to the bending angle error of each wrist-foot unit in the kth iteration process and the control quantity in the kth iteration process.
Optionally, the voltage magnitude applied to the driving element of the wrist-foot unit a during the (k + 1) th iteration is determined using the following formula:
wherein u is a,k+1 (t) is the magnitude of the voltage applied to the drive element of the wrist-foot unit a during the (k + 1) th iteration, u a,k (t) is the voltage applied to the driving element of the wrist-foot unit a during the kth iteration, phi is the proportional term gain coefficient, gamma is the differential term gain coefficient, e a,k (t) is the bending angle error of the wrist-foot unit a in the k iteration process,
is e a,k The differential of (t), t being the time.
Optionally, the 5 wrist-foot units are a first wrist-foot unit, a second wrist-foot unit, a third wrist-foot unit, a fourth wrist-foot unit and a fifth wrist-foot unit in turn clockwise;
one movement cycle comprises 7 moments; the desired trajectory is:
at the 1 st moment, the expected bending angles of the first wrist-foot unit, the second wrist-foot unit, the third wrist-foot unit, the fourth wrist-foot unit and the fifth wrist-foot unit are all 0 degree;
at the 2 nd moment, the expected bending angles of the first wrist-foot unit and the second wrist-foot unit are both 90 degrees, and the expected bending angles of the third wrist-foot unit, the fourth wrist-foot unit and the fifth wrist-foot unit are all 0 degree;
at the 3 rd moment, the expected bending angles of the first wrist-foot unit, the second wrist-foot unit, the third wrist-foot unit and the fifth wrist-foot unit are all 90 degrees, and the expected bending angle of the fourth wrist-foot unit is 0 degree;
at the 4 th moment, the expected bending angles of the first wrist-foot unit, the second wrist-foot unit, the third wrist-foot unit, the fourth wrist-foot unit and the fifth wrist-foot unit are all 90 degrees;
at the 5 th moment, the expected bending angles of the first wrist-foot unit and the second wrist-foot unit are both 0 degrees, and the expected bending angles of the third wrist-foot unit, the fourth wrist-foot unit and the fifth wrist-foot unit are all 90 degrees;
at the 6 th moment, the expected bending angles of the first wrist-foot unit, the second wrist-foot unit, the third wrist-foot unit and the fifth wrist-foot unit are all 0 degrees, and the expected bending angle of the fourth wrist-foot unit is 90 degrees;
at time 7, the desired bending angles of the first, second, third, fourth and fifth wrist-foot units are all 0 °.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the starfish-imitating soft robot comprises a supporting unit and 5 wrist-foot units, wherein the 5 wrist-foot units are connected with the supporting unit in a central symmetry manner, each wrist-foot unit comprises a driving element and an executing element, the executing element is made of a liquid crystal elastomer, and the driving element is attached to the upper surface of the executing element and is connected with an external power supply; the drive element is used for converting external power source's electric energy into heat energy to drive the executive component and take place bending deformation, imitative starfish software robot is based on 4D and prints, and each part comprises flexible material, and the compliance is good, has very strong environment adaptability, and simple structure, and the integration degree is high, and programmable ability is strong. In addition, the algorithm of the closed-loop PD type iterative learning control does not depend on a model, and the precise behavior control of the starfish-imitating soft body robot can be realized only according to input and output data.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a perspective view of a starfish-like soft robot based on 4D printing according to the present invention;
FIG. 2 is a schematic view of a single wrist-foot unit;
FIG. 3 is a schematic diagram of state 1 of a 4D printing starfish-like software robot in the process of moving according to the present invention;
FIG. 4 is a schematic diagram of state 2 of the 4D printing starfish-like soft robot in the motion process according to the present invention;
FIG. 5 is a schematic diagram of state 3 of the 4D printing starfish-like software robot in the process of moving;
FIG. 6 is a schematic diagram of state 4 of the 4D printing starfish-like software robot in the process of moving;
FIG. 7 is a schematic diagram of state 5 during the movement of the 4D printing starfish-like software robot of the present invention;
FIG. 8 is a schematic diagram of state 6 during the movement of the 4D printing starfish-like software robot of the present invention;
FIG. 9 is a schematic diagram of state 7 of the 4D printing starfish-like soft robot during movement according to the present invention;
FIG. 10 is a control flow chart of the starfish-like software robot based on 4D printing according to the present invention;
FIG. 11 is a flow chart of an iterative learning control algorithm;
FIG. 12 is a simulation diagram of a wrist-foot unit tracking a step trajectory in accordance with the present invention;
FIG. 13 is a simulation diagram of a tracking error of a wrist-foot unit on a step trajectory according to the present invention;
FIG. 14 is a simulation of the tracking of sinusoidal tracks by a wrist-foot unit of the present invention;
FIG. 15 is a diagram of a simulation of the tracking error of a wrist-foot unit on a sinusoidal trajectory in accordance with the present invention.
Description of the symbols:
the wrist-foot-driven type robot comprises a supporting unit-1, a first wrist-foot unit-21, a second wrist-foot unit-22, a third wrist-foot unit-23, a fourth wrist-foot unit-24, a fifth wrist-foot unit-25, a driving element-3, an actuating element-4 and a sensing element-5.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a starfish-imitating soft robot based on 4D printing and a control method thereof, which can realize accurate behavior control of the robot and enable the robot to have good passing capability on complex terrains such as sand, soil and the like.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Example one
As shown in fig. 1, the starfish-like soft robot based on 4D printing provided in this embodiment includes: support unit 1 and 5 wrist-foot units. The 5 wrist-foot units are a first wrist-foot unit 21, a second wrist-foot unit 22, a third wrist-foot unit 23, a fourth wrist-foot unit 24 and a fifth wrist-foot unit 25 in turn according to the clockwise direction. In the present embodiment, the supporting unit 1 is a double-layer polyimide film.
The 5 wrist-foot units are connected with the supporting unit 1 in a central symmetry shape. In this embodiment, each wrist-foot unit is connected with the support unit 1 in a central symmetry manner. Specifically, the shape of the supporting unit 1 is a regular pentagon. The wrist-foot units are all rectangular. One end of each wrist-foot unit is fixedly connected with one side of the supporting unit 1.
As shown in fig. 2, each wrist-foot unit includes a driving element 3 and an actuator 4. In the present embodiment, the material of the actuator 4 is LCE (liquid crystal elastomer). The actuator 4 is used to effect the flexion movement of each of said wrist-foot units.
The driving element 3 is attached to the upper surface of the actuator 4 and is connected to an external power source. The driving element 3 is used for converting the electric energy of an external power supply into heat energy by utilizing the electrothermal effect to cause temperature rise so as to drive the actuator 4 to generate bending deformation. In the present embodiment, the driving element 3 includes a polyimide film and a grid-shaped carbon nanotube. And the latticed carbon nano tubes are stamped on the surface of the polyimide film. That is, the driving element 3 is made of a polyimide film and a mesh-like carbon nanotube imprinted on the surface thereof.
Further, each wrist-foot unit further comprises a sensing element 5. The sensor element 5 is attached to the lower surface of the actuator 4. The sensor element 5 is used to detect the bending angle of the actuator 4. In the present embodiment, the sensor element 5 is a bending curvature sensor.
When the wrist-foot unit is energized by an external power supply, each actuator 4 is subjected to downward bending deformation by heat. When the energization is stopped, each actuator 4 is slowly restored to the initial state. Each sensor element 5 detects the bending angle during the bending deformation of each wrist-foot unit. Each wrist-foot unit can generate flexible bending deformation under the electric stimulation, and the crawling movement similar to starfish can be realized through the matching of a plurality of wrist-foot units.
All parts of the starfish-imitating soft robot based on 4D printing are made of flexible materials, the adaptability is good, the environment adaptability is strong, the complex environments such as sand, stone, soil and the like can be met in the crawling process, and the wrist-foot elements are made of flexible intelligent materials based on 4D printing, so that the starfish-imitating soft robot is low in manufacturing cost, simple in structure, high in integration degree and strong in programmability.
The motion cycle of the 4D printing starfish-imitating soft robot is mainly divided into the following seven states:
as shown in fig. 3, state 1: the starfish-like soft robot is in an initial state, wherein the first wrist-foot unit 21 and the second wrist-foot unit 22 face the advancing direction, and all the wrist-foot units are in an unpowered state and are kept horizontal.
As shown in fig. 4, state 2: the first wrist-foot unit 21 and the second wrist-foot unit 22 are electrified and bent to 90 degrees, and the friction force between the wrist-foot units and the ground is utilized to drive the robot to move forward.
As shown in fig. 5, state 3: the first wrist-foot unit 21, the second wrist-foot unit 22, the third wrist-foot unit 23 and the fifth wrist-foot unit 25 are electrified, namely 4 wrist-foot units positioned on the front side are electrified and are in a bending state, and the starfish-imitating soft body robot shows a forward tilting trend.
As shown in fig. 6, state 4: the first wrist-foot unit 21, the second wrist-foot unit 22, the third wrist-foot unit 23, the fourth wrist-foot unit 24 and the fifth wrist-foot unit 25 are electrified, all the wrist-foot units are in a bending state, and compared with the initial state, the gravity center of the starfish-like soft robot moves forwards.
As shown in fig. 7, state 5: the third wrist-foot unit 23, the fourth wrist-foot unit 24 and the fifth wrist-foot unit 25 are kept electrified and are in a bending state, the first wrist-foot unit 21 and the second wrist-foot unit 22 are stopped being electrified and gradually return to a flat state, and the center of gravity of the robot is pushed to move forwards by using the elastic potential energy accumulated in the bending process.
As shown in fig. 8, state 6: the fourth wrist-foot unit 24 is kept powered on, the third wrist-foot unit 23 and the fifth wrist-foot unit 25 are powered off, namely the four wrist-foot units positioned on the front side are powered off, and the starfish-like soft robot continuously moves forward.
As shown in fig. 9, state 7: the fourth wrist-foot unit 24 stops being electrified, the starfish-like soft robot returns to the initial state, a complete movement cycle is completed, and the whole motion is represented as forward motion.
Example two
In order to control the starfish-like soft robot based on 4D printing provided in the first embodiment, the present embodiment provides a control method of the starfish-like soft robot based on 4D printing.
Nowadays, an iterative learning control algorithm is widely applied to mechanical arm control, and has a set of relatively perfect theoretical system. The iterative learning control algorithm can realize complete tracking of any track, is simple, does not need an accurate mathematical model, and can realize accurate control of the system through continuous iteration and correction. For flexible intelligent materials, the model building is a difficult process, and the iterative learning control algorithm can realize accurate control of the robot by training and utilizing input and output data, so that the problem of difficult modeling is avoided. The invention adopts an iterative learning control algorithm independent of a model, and can realize accurate behavior control of the starfish-imitating software robot only according to input and output data.
As shown in fig. 10, the method for controlling a starfish-like soft robot based on 4D printing according to this embodiment includes:
s1: a desired trajectory is obtained. The desired trajectory includes a desired bend angle for each wrist-foot unit at each time during a cycle of motion. The desired trajectory is the final goal that the robot motion needs to achieve. The iterative learning control algorithm does not need an accurate mathematical model, and can realize the accurate tracking of any expected track according to the continuous iterative learning of input and output data.
S2: based on the expected track, the driving element of each wrist-foot unit is electrified through an external power supply to drive the executing element to generate bending deformation, and the voltage applied to the driving element of each wrist-foot unit is controlled by adopting a closed-loop PD type iterative learning method, so that each wrist-foot unit moves according to the expected track.
FIG. 11 is a control block diagram of an iterative learning control algorithm. The iterative learning control algorithm obtains the deviation of the output signal and the expected track by controlling and trying the control object, and continuously corrects the control signal by using the deviation and the control law, so that the error of the output signal at the new time is smallerAnd the system is circulated in such a way, the output of the system gradually approaches to the expected track, and the accurate control of the system is realized. U in FIG. 11 k-1 For the magnitude of the voltage applied to the driving element of the wrist-foot unit during the (k-1) th iteration, u k The magnitude of the voltage applied to the drive element of the wrist-foot unit during the kth iteration u k+1 The magnitude of the voltage applied to the driving element of the wrist-foot unit during the (k + 1) th iteration, y k-1 Is the actual bending angle, y, of the actuator during the (k-1) th iteration k Is the actual bending angle, y, of the actuator during the kth iteration d Is the desired bending angle of the wrist-foot unit, e k-1 Is the bending angle error of the wrist-foot unit in the k-1 iteration, e k For the bending angle error of the wrist-foot unit in the k-th iteration process, the control object is the voltage applied to the driving element of each wrist-foot unit.
Since the iterative learning control algorithm realizes continuous approximation of the expected track according to the increase of the iteration number, the algorithm has an integral effect. The invention removes an integral term, and selects a proportional term and a differential term to form a closed-loop PD type iterative learning method.
Specifically, the step S2 of controlling the voltage applied to the driving element of each wrist-foot unit by using a closed-loop PD type iterative learning method specifically includes:
and aiming at the kth iteration, acquiring the control quantity in the kth iteration process. The control amount is the magnitude of voltage applied to the driving element of each wrist-foot unit.
For any wrist-foot unit, detecting the actual bending angle y of the actuating element by the sensing element of the wrist-foot unit k (t)。
According to the actual bending angle y k (t) and desired bending angle y of said wrist-foot unit d (t) determining the bending angle error e of said wrist-foot unit during the kth iteration k (t) of (d). In particular, formula e is adopted k (t)＝y d (t)-y k (t) calculating a bend angle error.
And determining the control quantity in the (k + 1) th iteration process according to the bending angle error of each wrist-foot unit in the kth iteration process and the control quantity in the kth iteration process.
Specifically, the PD-type closed loop iterative learning control uses the bending angle error at the time of current control as a feedback term, and determines the magnitude of the voltage applied to the driving element of the wrist-foot unit a during the (k + 1) th iteration using the following formula:
wherein u is a,k+1 (t) is the magnitude of the voltage applied to the driving element of the wrist-foot unit a during the (k + 1) th iteration, u a,k (t) is the voltage applied to the driving element of the wrist-foot unit a during the kth iteration, phi is a proportional term gain coefficient, gamma is a differential term gain coefficient, e a,k (t) is the bending angle error of the wrist-foot unit a during the kth iteration,
is e a,k The differential of (t), t being the time.
The iterative learning algorithm continuously modifies the control quantity through gradual increase of iteration times, and then corrects the actual bending angle of the wrist-foot unit of the soft robot until accurate control of the starfish-like soft robot is achieved.
Further, before step S1, the method for controlling the starfish-like soft robot based on 4D printing further includes:
and electrifying each wrist-foot unit by utilizing an external power supply so as to change the bending angle of each wrist-foot unit. And measuring the bending angle corresponding to the resistance value at each moment by using the bending curvature sensor. And fitting the function by adopting a nonlinear least square method to obtain a relation equation of the resistance value of the bending curvature sensor and the bending angle of the wrist-foot unit. The bending angle of each wrist-foot unit can be further controlled.
Further, one movement cycle includes 7 moments. In the step S1, determining the action time sequence of each wrist-foot unit according to the forward moving principle of the 4D starfish-imitating soft robot to obtain the expected track:
at time 1, the desired bending angles of the first wrist-foot unit, the second wrist-foot unit, the third wrist-foot unit, the fourth wrist-foot unit and the fifth wrist-foot unit are all 0 °.
At the time 2, the desired bending angles of the first wrist-foot unit and the second wrist-foot unit are both 90 °, and the desired bending angles of the third wrist-foot unit, the fourth wrist-foot unit and the fifth wrist-foot unit are all 0 °.
At time 3, the desired bending angles of the first wrist-foot unit, the second wrist-foot unit, the third wrist-foot unit and the fifth wrist-foot unit are all 90 °, and the desired bending angle of the fourth wrist-foot unit is 0 °.
At time 4, the desired bending angles of the first, second, third, fourth and fifth wrist-foot units are all 90 °.
At the 5 th moment, the expected bending angles of the first wrist-foot unit and the second wrist-foot unit are both 0 degrees, and the expected bending angles of the third wrist-foot unit, the fourth wrist-foot unit and the fifth wrist-foot unit are all 90 degrees.
At time 6, the desired bending angles of the first wrist-foot unit, the second wrist-foot unit, the third wrist-foot unit and the fifth wrist-foot unit are all 0 °, and the desired bending angle of the fourth wrist-foot unit is 90 °.
At time 7, the desired bending angles of the first, second, third, fourth and fifth wrist-foot units are all 0 °.
The iterative learning control algorithm is applied to the 4D printing starfish-imitating soft robot structure, the control effect of the iterative learning control algorithm on a single wrist-foot unit of the 4D printing starfish-imitating soft robot is tested through a specific simulation experiment, and a step track and a sine track are adopted as an expected track. Fig. 12 and 13 are simulation diagrams of step trajectory tracking and tracking error of a wrist-foot unit according to the present invention, and fig. 14 and 15 are simulation diagrams of sinusoidal trajectory tracking and tracking error of a wrist-foot unit according to the present invention. The chain dotted lines in fig. 12 and fig. 14 represent the expected tracks of the wrist-foot unit, the solid lines represent the actual tracks of the wrist-foot unit, and it can be seen from the simulation results that the wrist-foot unit realizes accurate tracking of the step tracks and the sinusoidal tracks after multiple iterations. It can be seen in fig. 13 and 15 that as the number of iterations increases, the tracking error of the wrist-foot unit gradually decreases, and finally approaches to 0. The simulation research result shows the effectiveness of controlling the starfish-imitating software robot.
The invention realizes the accurate control of the 4D printing starfish-imitating soft robot by using the iterative learning control algorithm, and can realize the tracking of any track by using a simple algorithm, thereby avoiding the difficulty in flexible intelligent material modeling, overcoming the problem of difficulty in software robot modeling and improving the degree of freedom in software robot control.
In the present specification, the embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
The principle and the embodiment of the present invention are explained by applying specific examples, and the above description of the embodiments is only used to help understanding the method and the core idea of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the foregoing, the description is not to be taken in a limiting sense.
Claims (10)
1. The starfish-imitating soft robot based on 4D printing is characterized by comprising: a support unit and 5 wrist-foot units; the 5 wrist-foot units are connected with the supporting unit in a centrosymmetric manner;
each wrist-foot unit comprises a driving element and an executing element;
the material of the actuating element is a liquid crystal elastomer;
the driving element is attached to the upper surface of the execution element and is connected with an external power supply; the driving element is used for converting electric energy of an external power supply into heat energy so as to drive the actuating element to generate bending deformation.
2. The starfish-like soft robot based on 4D printing according to claim 1, wherein the supporting unit is a double-layer polyimide film.
3. The starfish-like soft robot based on 4D printing of claim 1, wherein each wrist-foot unit further comprises a sensing element;
the sensing element is attached to the lower surface of the actuating element; the sensing element is used for detecting the bending angle of the actuating element.
4. The starfish-like soft robot based on 4D printing of claim 3, wherein the sensing element is a bending curvature sensor.
5. The starfish-like soft robot based on 4D printing according to claim 1, wherein the driving element comprises a polyimide film and grid-shaped carbon nanotubes; and the latticed carbon nano tubes are imprinted on the surface of the polyimide film.
6. The starfish-like soft robot based on 4D printing of claim 1, wherein the shape of the supporting unit is a regular pentagon; the wrist-foot units are all rectangular;
one end of each wrist-foot unit is fixedly connected with one edge of the supporting unit respectively.
7. A control method of a starfish-imitating soft body robot based on 4D printing is used for controlling the starfish-imitating soft body robot based on 4D printing according to any one of claims 1-6, and is characterized in that the control method of the starfish-imitating soft body robot based on 4D printing comprises the following steps:
acquiring an expected track; the expected track comprises expected bending angles of the wrist-foot units at all times in one motion cycle;
based on the expected track, the driving element of each wrist-foot unit is electrified through an external power supply to drive the executing element to generate bending deformation, and the voltage applied to the driving element of each wrist-foot unit is controlled by adopting a closed-loop PD type iterative learning method, so that each wrist-foot unit moves according to the expected track.
8. The control method of the starfish-like soft robot based on 4D printing according to claim 7, wherein the method of closed-loop PD type iterative learning is used to control the voltage applied to the driving elements of each wrist-foot unit, and specifically comprises:
aiming at the kth iteration, acquiring a control quantity in the kth iteration process; the control quantity is the voltage applied to the driving element of each wrist-foot unit; 0-n k;
for any wrist-foot unit, detecting the actual bending angle of an actuating element through a sensing element of the wrist-foot unit;
determining the bending angle error of the wrist-foot unit in the kth iteration process according to the actual bending angle and the expected bending angle of the wrist-foot unit;
and judging whether the bending angle error of each wrist-foot unit in the kth iteration process is smaller than a set threshold value, if so, stopping iteration control, and otherwise, determining the control quantity in the (k + 1) th iteration process according to the bending angle error of each wrist-foot unit in the kth iteration process and the control quantity in the kth iteration process.
9. The control method of the starfish-like soft robot based on 4D printing according to claim 8, wherein the voltage applied to the driving element of the wrist-foot unit a during the k +1 th iteration is determined by the following formula:
wherein u is a,k+1 (t) is the magnitude of the voltage applied to the drive element of the wrist-foot unit a during the (k + 1) th iteration, u a,k (t) is the voltage applied to the driving element of the wrist-foot unit a during the kth iteration, phi is the proportional term gain coefficient, gamma is the differential term gain coefficient, e a,k (t) is the bending angle error of the wrist-foot unit a during the kth iteration,
is e a,k The differential of (t), t being the time.
10. The control method of the starfish-imitated soft robot based on 4D printing according to claim 7, wherein the 5 wrist-foot units are a first wrist-foot unit, a second wrist-foot unit, a third wrist-foot unit, a fourth wrist-foot unit and a fifth wrist-foot unit in a clockwise order;
one movement cycle comprises 7 moments; the expected trajectory is:
at the 1 st moment, the expected bending angles of the first wrist-foot unit, the second wrist-foot unit, the third wrist-foot unit, the fourth wrist-foot unit and the fifth wrist-foot unit are all 0 degree;
at the 2 nd moment, the expected bending angles of the first wrist-foot unit and the second wrist-foot unit are both 90 degrees, and the expected bending angles of the third wrist-foot unit, the fourth wrist-foot unit and the fifth wrist-foot unit are all 0 degree;
at the 3 rd moment, the expected bending angles of the first wrist-foot unit, the second wrist-foot unit, the third wrist-foot unit and the fifth wrist-foot unit are all 90 degrees, and the expected bending angle of the fourth wrist-foot unit is 0 degree;
at time 4, the expected bending angles of the first wrist-foot unit, the second wrist-foot unit, the third wrist-foot unit, the fourth wrist-foot unit and the fifth wrist-foot unit are all 90 degrees;
at the 5 th moment, the expected bending angles of the first wrist-foot unit and the second wrist-foot unit are both 0 degrees, and the expected bending angles of the third wrist-foot unit, the fourth wrist-foot unit and the fifth wrist-foot unit are all 90 degrees;
at the 6 th moment, the expected bending angles of the first wrist-foot unit, the second wrist-foot unit, the third wrist-foot unit and the fifth wrist-foot unit are all 0 degrees, and the expected bending angle of the fourth wrist-foot unit is 90 degrees;
at time 7, the desired bending angles of the first, second, third, fourth and fifth wrist-foot units are all 0 °.
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