Facial expression driving system and method based on bionic muscle structure

Abstract

The invention belongs to the technical field of robots, and particularly relates to a bionic muscle structure-based facial expression driving system and method.The facial expression driving system comprises a flexible skin layer, a driving layer and a control system which are integrally formed; tendon simulation pieces are pre-buried in the muscle simulation area; drivers of the driving layer are intensively arranged in the robot head shell, pull the tendon simulation piece through a low-friction catheter and a transmission mechanism, drive the muscle simulation area to directionally deform and link the skin simulation area; the control system controls the driver by taking the expression unit as an object based on the facial action unit instruction library; the invention further discloses a robot applying the system and a manufacturing method of the flexible skin. The head structure is simplified, facial expressions with richer natural expressions are generated with less driving input, and the expression naturalness and the system stability are improved.

Description

Technical Field

[0001] This invention belongs to the field of robotics technology, specifically relating to a facial expression driving system and method based on biomimetic muscle structure. Background Technology

[0002] With the development of humanoid robot technology, the requirements for the naturalness and richness of facial expressions are becoming increasingly stringent. In existing technologies, the driving of robot facial expressions mostly adopts a "single-point drive" mode, that is, a single actuator controls the displacement of a single point. However, this method can lead to stiff and mechanical expressions. Furthermore, a large number of actuators results in a complex robot head structure, increased weight, high power consumption, and complex control algorithms. In addition to increasing costs, the numerous moving parts also reduce the stability of the system.

[0003] Therefore, there is an urgent need for a facial expression driving system and method that can generate richer and more natural expressions with less driving input. Summary of the Invention

[0004] This invention provides a facial expression driving system and method based on biomimetic muscle structure, which can generate richer and more natural facial expressions with less driving input.

[0005] In a first aspect, the present invention provides a facial expression driving system based on a biomimetic muscle structure, comprising: The flexible skin layer is an integrally molded elastomer, comprising at least one muscle simulation area and a skin simulation area located between adjacent muscle simulation areas; at least one tendon simulation element is pre-embedded in the muscle simulation area, one end of the tendon simulation element is fixed in the muscle simulation area, and the other end extends to the outside of the flexible skin layer and connects to the driving layer. The driving layer includes a driver and a transmission mechanism; the driver pulls the tendon simulator through the transmission mechanism to drive the muscle simulation area to deform in a directional manner, thereby driving the adjacent skin simulation area to deform synchronously. The control system, connected to the driver layer, is used to receive facial expression commands and call the pre-stored facial expression command library containing facial motion units to control the driver.

[0006] Optionally, the shape and spatial distribution of the muscle simulation area correspond to the facial muscles in human facial anatomy.

[0007] Optionally, the local thickness of the muscle simulation area is greater than that of the skin simulation area, and the Shore hardness of the material used in the muscle simulation area is higher than that of the skin simulation area.

[0008] Optionally, the muscle simulation area uses a flexible material with a Shore A hardness of 20-30; the skin simulation area uses a flexible material with a Shore A hardness of 00-10.

[0009] Optionally, the tendon simulator is a flexible cable, and its embedding direction in the muscle simulation area is consistent with the contraction direction of the facial muscles simulated in that area; the end of the tendon simulator away from the driving layer is fixed to the side of the muscle simulation area near the facial expression action point through an embedded anchoring structure.

[0010] Optionally, the drive layer also includes a low-friction conduit disposed inside the robot head shell; the tendon simulator passes through the low-friction conduit and is linked to the transmission mechanism, which includes at least one of a pulley block, a linkage, or a cable retraction assembly.

[0011] Optionally, the control system has a built-in facial motion unit database; the facial motion unit database contains driver displacement combination logic corresponding to basic expressions; the control system controls multiple muscle simulation areas to deform collaboratively by calling different driver displacement combination logics to generate complex expressions.

[0012] Secondly, the present invention provides a highly realistic humanoid robot, including a robot head shell and the aforementioned facial expression driving system based on bionic muscle structure installed on the robot head shell.

[0013] Thirdly, the present invention provides a method for manufacturing flexible skin in the aforementioned facial expression driving system based on biomimetic muscle structure, comprising the following steps: A biomimetic mold with a specific cavity is provided, the cavity having a muscle area cavity corresponding to the distribution of human facial muscles; The tendon simulator was implanted into the cavity of the muscle area and its end was fixed. Injecting a first flexible material into the cavity of the muscle region; A second flexible material is injected into the remaining cavity areas of the biomimetic molding mold; After curing, it forms a flexible skin layer that is integrally molded and includes muscle simulation areas and skin simulation areas; The first flexible material has a higher hardness after curing than the second flexible material.

[0014] Beneficial effects: 1. By mimicking the anatomical structure of the human face, the shape and distribution of the muscle simulation area and the embedding direction of the tendon simulation parts are all in line with the shape and contraction rules of real facial muscles. Combined with the difference in hardness and thickness between the muscle simulation area and the skin simulation area, the directional deformation of the muscle simulation area can drive the adjacent skin simulation area to produce natural skin details such as stretching, depression or wrinkling. This gets rid of the mechanical feeling of traditional single-point drive and realizes the surface linkage deformation that conforms to the laws of biomechanics, so that the expression is closer to the real human state.

[0015] 2. By centrally arranging the actuators and low-friction conduits inside the robot's head shell, the design defects of densely arranging actuators under the facial skin are avoided, significantly reducing the number of actuators. This not only simplifies the mechanical structure of the robot's head and reduces the overall weight, but also reduces system power consumption and control complexity. At the same time, the actuators and transmission components are effectively protected by the head shell, reducing external impacts and environmental interference. Combined with the embedded anchoring structure of the tendon simulation component, the failure probability of moving parts is reduced, significantly improving the stability and service life of the system.

[0016] 3. The control system takes the facial expression unit as the core control object and has a built-in facial expression instruction library based on the facial motion coding system. This eliminates the need for independent programming of individual skin points, simplifying the design and debugging process of the control algorithm. It also supports direct calling of basic expressions and combined editing of complex expressions, improving the flexibility and development efficiency of expression creation. In addition, the reduction in the number of drivers, the one-piece flexible skin manufacturing process, and the standardized configuration of components effectively reduce the manufacturing cost and assembly difficulty of the system.

[0017] 4. The flexible skin layer adopts a one-piece molding process with dual-hardness materials, and the muscle simulation area and skin simulation area are tightly combined without splicing gaps, ensuring the continuity of deformation transmission; the tendon simulation component is directly embedded and fixed during the molding process, avoiding the complex process of subsequent assembly, while improving the connection between the tendon and the skin layer. It is not easy to loosen and fall off under long-term traction, further ensuring the reliability and stability of the system in long-term operation. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of a facial expression driving system based on a biomimetic muscle structure according to the present invention; Figure 2 This is a schematic diagram of the structure of the flexible skin layer of the present invention; Figure 3 This is a schematic diagram of the structure of the muscle simulation area and tendon simulation component of the present invention; The reference numerals in the accompanying drawings include: 1. Flexible skin layer; 11. Muscle simulation area; 11a. Frontalis muscle simulation area; 11b. Corrugator supercilii muscle simulation area; 11c. Orbicularis oculi muscle simulation area; 11d. Zygomaticus major muscle simulation area; 11e. Orbicularis oris muscle simulation area; 11f. Depressor anguli oris muscle simulation area; 12. Skin simulation area; 13. Tendon simulation component; 2. Drive layer; 21. Actuator; 22. Transmission mechanism; 3. Robot head shell; 4. Control system. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "inner," and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present application. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0022] In the description of this invention, unless otherwise explicitly specified and limited, the term "connection" or similar designation indicating a connection between components should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral part; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0023] Currently, most methods for driving facial expressions in robots employ a "single-point drive" approach, where a single actuator controls the displacement of a single point. However, this method results in stiff, mechanical expressions. Furthermore, a large number of actuators leads to a complex robot head structure, increased weight, higher power consumption, and more complex control algorithms, increasing costs and reducing system stability due to numerous moving parts. Therefore, this application discloses a facial expression driving system and method based on biomimetic muscle structures, capable of generating richer and more natural facial expressions with less driving input.

[0024] See Figure 1 As shown, a facial expression driving system based on biomimetic muscle structure includes a flexible skin layer 1, a driving layer 2, and a control system 4.

[0025] Specifically, the flexible skin layer 1 is manufactured as an elastomer using a one-piece molding process, comprising a muscle simulation area 11 and a skin simulation area 12. The skin simulation area 12 is located between adjacent muscle simulation areas 11, forming a complementary structural distribution. The shape and spatial distribution of the muscle simulation areas 11 strictly correspond to the facial expression muscles in human facial anatomy, such as... Figure 2 , Figure 3 The diagram illustrates the distribution of the following muscle simulation areas: frontalis muscle simulation area 11a, corrugator supercilii muscle simulation area 11b, orbicularis oculi muscle simulation area 11c, zygomaticus major muscle simulation area 11d, orbicularis oris muscle simulation area 11e, and depressor anguli oris muscle simulation area 11f. The frontalis muscle simulation area 11a corresponds to a fan-shaped distribution on the forehead; the zygomaticus major muscle simulation area 11d corresponds to a band-like distribution extending from the cheekbone to the corner of the mouth; and the corrugator supercilii muscle simulation area 11b corresponds to a narrow, vertical structure located between the eyebrows. This precise biomimetic layout lays the structural foundation for the natural presentation of facial expressions. Those skilled in the art should understand that the muscle simulation areas 11 are not limited to the above example and can also encompass other facial expression muscle areas based on facial anatomy.

[0026] like Figure 3 As shown, the local thickness of the muscle simulation area 11 is greater than that of the skin simulation area 12, and the flexible material used has a higher Shore hardness than that of the skin simulation area 12. Specifically, the muscle simulation area 11 uses a flexible silicone material with a Shore A hardness of 20-30. Materials in this hardness range have both rigidity and elasticity, which can efficiently transmit tensile force and maintain deformation stability, ensuring effective force transmission during the stretching process. The skin simulation area 12 uses a flexible silicone material with a Shore A hardness of 00-10. This material is soft and easily deformable. When the muscle simulation area 11 deforms, it can simultaneously produce stretching, depression or wrinkling, naturally restoring the detailed features of human facial skin during facial expression changes, avoiding the mechanical feel of facial expressions.

[0027] At least one tendon simulator 13 is pre-embedded in the muscle simulation area 11. The tendon simulator 13 is made of a high-strength, low-elongation flexible cable, and its material can be ultra-high molecular weight polyethylene or carbon fiber composite material, which ensures sufficient tensile strength and reduces the impact of its own deformation on the accuracy of facial expressions. The embedding direction of the tendon simulator 13 in the muscle simulation area 11 is consistent with the contraction direction of the facial muscles simulated in that area. For example, the tendon simulator 13 corresponding to the zygomaticus major muscle extends from the corner of the mouth to the ear along the contraction direction of the zygomaticus major muscle, and the tendon simulator 13 corresponding to the frontalis muscle is arranged vertically upward along the contraction direction of the frontalis muscle, ensuring that the muscle simulation area 11 can produce directional deformation that conforms to the laws of biomechanics when stretched.

[0028] The tendon simulator 13 is fixed at one end away from the driving layer 2 by an embedded anchoring structure to the side of the muscle simulation area 11 near the facial expression action point. The embedded anchoring structure can increase the contact area between the tendon simulator 13 and the internal material of the muscle simulation area 11, improve the fixation firmness, avoid loosening or falling off during long-term traction, and ensure the stability and reliability of power transmission. The other end of the tendon simulator 13 extends to the outside of the flexible skin layer 1 and establishes a connection with the driving layer 2, serving as the interface for power transmission.

[0029] like Figure 1 As shown, the drive layer 2 includes a driver 21, a transmission mechanism 22, and a low-friction conduit. The driver 21 can be a micro servo motor or a linear servo motor. Both the driver 21 and the low-friction conduit are located inside the robot head shell 3. This layout not only protects the driver 21 and the low-friction conduit from external impacts and dust, but also avoids the structural complexity and increased weight caused by placing the driver 21 directly under the facial skin. At the same time, it simplifies the mechanical structure of the facial area and reduces the probability of failure.

[0030] The low-friction conduit can be made of high-density polyethylene or fluoropolymer, which can reduce frictional loss between the tendon simulator 13 and the inner wall of the conduit, improve transmission efficiency, and protect the surface of the tendon simulator 13, extending its service life. The tendon simulator 13 passes through the low-friction conduit and is linked with the transmission mechanism 22. The low-friction conduit can constrain the direction of the tendon simulator 13, preventing the tendon simulator 13 from deviating or tangling during traction, and ensuring precise orientation of power transmission.

[0031] The transmission mechanism 22 can be selected from at least one of pulley blocks, connecting rods, or cable retraction components, and can be flexibly configured according to the driving needs of different facial areas. When a pulley block is selected, the direction of force can be changed to effectively pull the tendon simulator 13 at different positions, which is especially suitable for driving the facial edge area; when a connecting rod is selected, the rotational motion of the actuator 21 can be converted into a stable linear pulling action, improving the uniformity of the pulling force; when a cable retraction component is selected, the tendon simulator 13 can be controlled to precisely adjust the pulling displacement. The above transmission mechanisms can be used alone or in combination to adapt to the driving needs of different facial areas with limited space. The core function of the transmission mechanism 22 is to convert the output motion of the actuator 21 into a linear pulling or releasing action on the tendon simulator 13, ensuring that the driving force can be efficiently and stably transmitted to the muscle simulation area 11.

[0032] The control system 4 establishes an electrical connection with the driver layer 2 to achieve bidirectional signal transmission and execution of control commands. The control system 4 has a built-in facial motion unit database, which is constructed based on the facial motion coding system and contains the driver displacement combination logic corresponding to basic expressions such as smiling, frowning, surprise, sadness, anger, and calmness.

[0033] When the control system 4 receives external expression commands, it calls the pre-stored facial motion unit expression command library to parse the high-level expression commands into corresponding control signals. For basic expressions, the control system 4 directly calls the corresponding driver displacement combination logic to control one or more drivers 21 to move according to preset parameters. For complex expressions, the control system 4 supports expression unit combination editing. By calling the driver displacement combination logic corresponding to different facial motion units, it controls multiple muscle simulation areas 11 to deform collaboratively, thereby generating custom complex expressions. This control method uses expression units as the controlled objects, eliminating the need for independent programming of individual skin points, simplifying the control logic, improving the flexibility and efficiency of expression creation, and ensuring the coordination and naturalness of the expressions.

[0034] As a specific embodiment, when simulating a "surprised" expression, the control system synchronously drives the frontalis muscle simulation area 11a to pull upward, and coordinates with the control of the orbicularis oculi muscle simulation area 11c to relax. Through the hardness difference between the muscle simulation area 11 and the skin simulation area 12, a horizontal fold is naturally formed on the forehead.

[0035] This embodiment also discloses a highly realistic humanoid robot, which includes a robot head shell 3 and the aforementioned facial expression driving system based on biomimetic muscle structure mounted on the robot head shell 3. During assembly, the edge of the flexible skin layer 1 is first fixed to the robot head shell 3 to ensure that the flexible skin layer 1 can deform freely under tension and is reliably fixed; then, the tendon simulation component 13 is passed through the low-friction conduit inside the robot head shell 3 and precisely connected to the transmission mechanism 22; finally, the actuator 21 is electrically connected to the control system 4 to complete the assembly of the entire system, enabling the robot to present natural facial expressions.

[0036] The following provides a detailed description of the manufacturing method of the flexible skin layer 1. This method is applied to the aforementioned facial expression driving system based on biomimetic muscle structures. The specific steps are as follows: Step S1: Provide a biomimetic molding mold with specific cavities. The cavities of the mold are designed according to the distribution characteristics of human facial muscles. They include muscle area cavities corresponding to each expression unit. The shape, direction and thickness of the muscle area cavities are completely consistent with the preset muscle simulation area 11. The remaining cavity areas of the mold correspond to the skin simulation area 12.

[0037] Step S2: The tendon simulator 13 is implanted into the muscle area cavity. The orientation of the tendon simulator 13 is consistent with the direction of the simulated muscle contraction corresponding to the muscle area cavity. At the same time, the distal end of the tendon simulator 13 is fixed in the preset position of the muscle area cavity by a positioning fixture.

[0038] Step S3: Inject the first flexible material into the cavity of the muscle area. The first flexible material is liquid silicone with a Shore A hardness of 20-30. After the first flexible material is semi-cured, the prototype structure of the muscle simulation area 11 is formed.

[0039] In step S4, a second flexible material is injected into the remaining cavity areas of the biomimetic molding mold. The second flexible material is a liquid silicone with a Shore A hardness of 00-10. This material has good fluidity and can fully fill the remaining space of the mold, achieving a tight bond with the initially cured first flexible material and avoiding delamination.

[0040] Step S5: The mold containing the two flexible materials is solidified to form an integral structure. After solidification, the mold is demolded to obtain an integrally formed flexible skin layer 1. The flexible skin layer 1 has a muscle simulation area 11 and a tendon simulation component 13 embedded in it. The muscle simulation area 11 and the skin simulation area 12 are naturally connected to form a surface domain linkage structure corresponding to the expression unit, which can achieve coordinated deformation under the pull of the tendon simulation component 13.

[0041] In this embodiment, through the above-mentioned structural design and manufacturing process, the facial expression driving system based on the bionic muscle structure can operate efficiently. The driver 21 is linked with the tendon simulation component 13 through the transmission mechanism 22, which pulls the muscle simulation area 11 to deform in a specific direction, thereby driving the adjacent skin simulation area 12 to deform synchronously. The control system 4 controls multiple drivers 21 to work together by calling the logical instructions in the facial action unit database, so that the flexible skin layer 1 can present natural and rich facial expressions.

[0042] The above are merely embodiments of the present invention. Commonly known structures and characteristics of the solutions are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, based on the guidance provided in this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. A facial expression driving system based on biomimetic muscle structure, characterized in that, include: The flexible skin layer (1) is an integrally formed elastomer, including at least one muscle simulation area (11) and a skin simulation area (12) located between adjacent muscle simulation areas (11); at least one tendon simulation element (13) is pre-embedded in the muscle simulation area (11), one end of the tendon simulation element (13) is fixed in the muscle simulation area (11), and the other end extends to the outside of the flexible skin layer (1) and connects with the driving layer (2); The driving layer (2) includes a driver (21) and a transmission mechanism (22); the driver (21) pulls the tendon simulator (13) through the transmission mechanism (22) to drive the muscle simulation area (11) to deform in a specific direction, thereby driving the adjacent skin simulation area (12) to deform synchronously; The control system (4) is connected to the driving layer (2) to receive facial expression instructions and call the facial expression instruction library with pre-stored facial motion units to control the driver (21).

2. The facial expression driving system based on bionic muscle structure as described in claim 1, characterized in that: The shape and spatial distribution of the muscle simulation area (11) correspond to the facial muscles in human facial anatomy.

3. The facial expression driving system based on biomimetic muscle structure as described in claim 1, characterized in that: The local thickness of the muscle simulation area (11) is greater than that of the skin simulation area (12), and the Shore hardness of the material used in it is higher than that of the skin simulation area (12).

4. The facial expression driving system based on biomimetic muscle structure as described in claim 3, characterized in that: The muscle simulation area (11) is made of a flexible material with a Shore A hardness of 20-30; the skin simulation area (12) is made of a flexible material with a Shore A hardness of 00-10.

5. The facial expression driving system based on biomimetic muscle structure as described in claim 1, characterized in that: The tendon simulator (13) is a flexible cable, and its embedding direction in the muscle simulation area (11) is consistent with the contraction direction of the facial muscles simulated in that area; the end of the tendon simulator (13) away from the driving layer (2) is fixed to the side of the muscle simulation area (11) near the facial expression action point through an embedded anchoring structure.

6. The facial expression driving system based on bionic muscle structure as described in claim 1, characterized in that: The drive layer (2) also includes a low-friction conduit disposed inside the robot head shell (3); the tendon simulator (13) passes through the low-friction conduit and is linked with the transmission mechanism (22), the transmission mechanism (22) including at least one of pulley block, linkage or cable retraction assembly.

7. The facial expression driving system based on bionic muscle structure as described in claim 1, characterized in that: The control system has a built-in facial motion unit database; the facial motion unit database contains driver displacement combination logic corresponding to basic expressions; the control system (4) controls multiple muscle simulation areas (11) to deform in coordination by calling different driver displacement combination logics to generate composite expressions.

8. A highly realistic humanoid robot, characterized in that, Includes a robot head shell (3), and a facial expression driving system based on any one of claims 1-7, mounted on the robot head shell (3).

9. A method for manufacturing flexible skin for a facial expression driving system based on biomimetic muscle structure as described in claim 1, characterized in that, Includes the following steps: A biomimetic mold with a specific cavity is provided, the cavity having a muscle area cavity corresponding to the distribution of human facial muscles; The tendon simulator (13) was implanted into the cavity of the muscle area and its end was fixed. Injecting a first flexible material into the cavity of the muscle region; A second flexible material is injected into the remaining cavity areas of the biomimetic molding mold; After curing, a flexible skin layer (1) is formed in one piece, including a muscle simulation area (11) and a skin simulation area (12). The first flexible material has a higher hardness after curing than the second flexible material.

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