| Coexisting-Cooperative-Cognitive Robots(Tri-Co Robots),one of the most important research directions in the field of robots,is a kind of robot that can interact with the operating environment,humans,and other robots naturally and they can also autonomously adapt to complex dynamic environments,and work collaboratively.Traditional rigid actuators such as motors and cylinders are difficult to meet Tri-Co Robots’ requirements which is safe human-machine-environment interaction,while soft actuators made of low-modulus materials have the characteristics of high flexibility and are suitable for realizing complex human-machine-environment interaction.Commonly used soft actuators include soft actuators based on electroactive polymer,shape memory material,and fluid pressure,which can achieve output characteristics similar to biological muscles and meet the driving requirements of Tri-Co Robots to a certain extent.However,soft actuators based on electroactive polymer have the disadvantage of high driving voltage,soft actuators based on shape memory material have the problem of poor output linearity,and soft actuators based on fluid pressure have the limitation of the large volume of air source device.These problems limit their further application in the field of Tri-Co Robots.The twisted artificial muscle(TAM)made of nylon 66 is a kind of soft actuator with low driven voltage,high output linearity,and excellent embeddability.It has great development potential to drive soft robots.Through analyzing the research status of the TAM,it still has the problem of lack of performance analysis model,low output force,complex control system,and no obvious advantages in the application of deformation mechanisms and locomotion robots.To promote the development of TAM in the field of soft driving,we established a static model to describe the relationship between the temperature output force and the TAM and lay a theoretical foundation for the output force enhancement research of the TAM.The TAM output force enhancement method based on multi-fiber coiling was proposed to explore the fabrication process of large output force TAM,and multi-twisted artificial muscle(MTAM)with large output force was fabricated.The combination process of metal heating wire and nylon 6,6 fiber was explored,and the method of realizing temperature self-sensing by using the impedance change of metal heating wire is proposed,which realizes the closed-loop control of temperature and deformation of the TAM.Finally,a temperature deformation mechanism,a tensegrity robot,a sixlegged soft robot,and a soft jumping robot driven by the TAM were developed to show the advantages and application potential of the TAM.The static model of TAM was established,including the temperature-untwisting torque model describing the thermal untwisting torque of the twisted fiber,the temperature-output force model describing the output force of the TAM,and the temperature-deformation model describing the deformation of the TAM.The output force error and deformation error between the calculation results of the model and the experimental results are less than 0.23 N and 0.5 mm,respectively.The static model showed the influence law of structural parameters and the TAM performance,which lays a theoretical foundation for the output force enhancement research of the TAM.The output force enhancement method based on multi-fiber coiling was proposed,and the production process of MTAM was explored.Through the bionic analysis of the biological skeletal muscle structure,we imitated its tightly parallel combination and twisted multiple fibers into a single fiber bundle after tightly parallelization to improve the untwisting torque of the TAM.The self-coiling fabrication process of the spiral structure generated by the twisted fiber bundle was explored,and the MATM was produced to improve the output force.Experimental results showed that,compared with the traditional single-twisted artificial muscle(STAM),the MATM increased by 4.4 times,2.4 times,and 33% for the untwisting torque,output force,and deformation rate,respectively.For the controlling requirement of the TAM,the method of realizing temperature self-sensing by using the impedance change of metal heating wire was proposed,and the closed-loop control of temperature and deformation of the TAM was realized.The process of metal heating wire tightly-wrapped on TAM was explored and the fitting algorithm between the resistance and temperature of metal heating wire was established.The resistance temperature fitting algorithm was combined with the tightly-wrapped process of the metal heating wire on the TAM fiber to realize the temperature self-sensing of TAM,and the self-sensing resolution range is0.03°C～0.04°C.Based on the temperature self-sensing method,the closed-loop control system of TAM was established,and a relative control accuracy of 1.8% is achieved.The temperature self-sensing method was applied to the MTAM,and a selfsensing MTAM is developed,which considers both large output force and high controllability.The temperature deformation mechanisms with large load capacity and soft locomotion robots with high motion flexibility were developed by using the new types of TAMs.Firstly,the MTAM with large output force was selected as the actuator,by combining with the six-bar tension structure,a folding deformation mechanism that could fold automatically with the increase of temperature under large load was developed and an extending deformation mechanism that could extend automatically with the increase of temperature was developed,which expand the application field of TAM.On this basis,by using self-sensing MTAM with the characteristic of high controllability and large output force,combined with a threebar tensegrity structure,a crawling tensegrity robot with straight and turning motion ability was developed,which provides a reference for the design of locomotion robots with high flexibility and large load ability.To improve the motion flexibility of the soft locomotion robot,a soft hexapod robot driven by self-sensing MTAM was developed,which realized the flexible motion with straight and turning ability.Finally,by using a self-sensing STAM with high controllability and small volume,combined with the thin-walled flexible bistable mechanism,a soft jumping robot with a pure flexible substrate was realized,and the performance advantages and application potential of the new fabricated TAMs were demonstrated. |
PDF Full Text Request