Design And Implementation Of Flexible Curvature Sensing Unit For Soft Pneumatic Actuators

Soft robots are developing vigorously in various fields because of its characteristics of the intrinsically soft and bio-compatible materials,diverse configurations,and clean power source.However,it encounters many problems,such as hysteresis,creep and underactuated process caused by flexible materials.Because of these disadvantages,the modeling and calculation of soft robot are complicated,and the sensor information is difficult to extract.Therefore,a spiral strain sensor with high linearity and a columnar strain sensor with high sensitivity are designed to solve the problem of lacking shape information of existing soft robots.In this paper,the shape information of pneumatic actuator is extracted by integrating the sensor with the external adhesion method,bringing a new solution to achieve curvature information.Firstly,the configurations and deformation mechanism of the pneumatic actuator are analyzed.At the same time,a soft actuator with embedded cavities was manufactured based on meshing method,and the influence of the number of air cavities is analyzed.By analyzing its manufacturing method,the mold configuration of soft robot was optimized based on the original perfusion method,and the manufacturing efficiency was improved.Secondly,a mixture of carbon nanotubes and silicone elastomer was used to fabricate conductive fibers by mechanical extrusion to ensure the stability of the sensor.By winding the conductive fiber,the service life and linearity of the sensor can be improved.The hysteresis,tensile performance,and creep characteristics of the proposed spiral sensor were measured,and the influence of the clamping force of the experimental device on the experimental results during the tensile test was analyzed.Then,a kind of elastic column with high adhesion was manufactured by using 3Dprinted mold and silicone elastomer.By comparing the coating properties of different carbon-based materials on the base column,a column strain sensor that can consider both wide measurement range and high sensitivity was selected and determined.Aiming at the problem of stress relaxation effect of viscoelastic materials,different driving methods are used to carry out experiments and avoid the problem of signal mutation caused by stress relaxation.Finally,a high linearity sensor was integrated into the outer surface of the end four chambers of the single-degree-of-freedom flexible pneumatic actuator to detect the curvature of the cylindrical object.It was proved that the sensor could detect the curvature of the cylindrical object without interacting with the inner surface of the object.A high sensitivity column sensor is integrated on the outer surface of the four chambers at the end of the soft actuator to test the actuation situation,which demonstrates the effectiveness of the sensor in representing the bending state of the pneumatic actuator.In this paper,a thin film strain sensor was proposed for the soft actuator with embedded cavities,and its sensing mechanism and fabrication process were analyzed.The sensor was integrated on the outer surface of the soft actuator with embedded cavities,demonstrating the effectiveness of the thin film sensor in expressing the bending state of the soft actuator.An endoscope is integrated on the inner surface of the actuator for driving experiments,which shows the superiority of the external integrated sensor and the effectiveness of the proposed soft actuator as an endoscope with active bending ability.