Research On Software Air Vehicles Based On Soft Actuators

The helicopter cannot fly at the height from 0 to 300 m by the aviation law.Natural disasters and vegetation information on the ground need to be observed and photographed from the air conveniently,therefore,controllable flight devices close to the ground are demanded urgently.Wireless controllable helium balloon system has characteristics of carrying heavy things,long battery life,low cost and noise,fast responds,energy saving and safe operating.Although some progress has been made on the bionics application,the understanding of the flight mechanism based on dielectric elastomer actuators(DEA)is not sufficient.Design the reasonable structures and movement rules,carry out theoretical computation and experimental research,analyze the force,power and other key issues for the robot,all which will help to develop the flight mechanism and provide references for the soft-drive vehicles in the future.The flight robot base on DEA could realize the up and down,rotational and translational motion.Theoratical models were established;The resistance and the trajectory were studied through experimental measurements and theoretical simulation.Main contents and conclusions are as follows:(1)Study on the reasonable structure and volume change of balloon actuators with electromechanical properties and carrying capacity.An information collection platform was built,meanwhile,high-speed cameras were used.The critical data of parameters were obtained after the software analysis and calculation.A flying robot system based on DEA was established;Formulas were derived to describe real-time variations of pretension,such as voltage,pressure,charge and volume.The variation of the Helmholtz free energy equals the work done by voltage,pressure and the inertia;Combining with the Maxwell stress,models with key parameters are obtained.Under the effect of electric field,the electromechanical instability and electric breakdown phenomena exist on the DE film.Electric breakdown relates to the prestretch;With increasing voltage,the electromechanical instability happened,wrinkles formed either near the clamped edge or the top part in the inflated balloon,the pre-stretch coefficient λpre was 3 to 6,the voltage φ was greater than 5.5 kV.(2)Unstable phenomena on the DE surface,such as loss of tension and electric breakdown.In order to imitate biological adhesion performance and skin properties,dielectric elastomers applied high voltages are used.A DE membrane could undergo wrinkles or bulging from the flat state when critical voltage was applied.Parameters in the calculating model were obtained by fitting experimental records.Four experimental phenomena were found out before electric breakdown in membranes that were supported by a circular frame:The active region in a membrane expanded against the passive region,the membrane was still flat till breakdown;Bulging formed on the membrane;Wrinkles and bulging coexisted;Wrinkles formed without bulging.Additionally,in the fourth state,two types of transition between flat regions and wrinkled regions were observed:①Wrinkles formed in small regions,then they grew at the expense of flat regions until the entire active region became wrinkled,the process was continuous;②Both wrinkled and flat regions moved interchangeably on the membrane till breakdown.It is found that the prestretch affects electromechanical phase transitions significantly.(3)The structural design of DE balloon actuators for large deformation.When a DE spherical shell is subject to an electric field through its thickness,it expands in radial direction and contracts in thickness.On the experimental platform,pressure and displacement sensors were used to measure DE balloon flight systems.The parameters affecting the buoyancy force,such as expansion amplitude and vibration frequency of soft spherical shells,were presented and analyzed.Based on theoretical analysis,some spherical structures filling with helium or air were designed.The main conclusions of these studies include:①Under the same pressure,the volume of a DE helium balloon is smaller than an air balloon;②Large deformation is very important for controlling DEA robots,we can increase the initial volume,electrode density and preloads to achieve this aim;③The greater volume changes,the more weight can be taken by a helium balloon,and the more buoyancy force could be controlled.By analyzing the dynamic behavior of spherical shells,the thick ones deformed smaller than thin shells.Finally,A large number of experiments demonstrated the feasibility of the controllable flight robot based on DEAs.(4)Based on DE balloon actuators,the buoyancy,the resistance and power consumption of the robot were studied.Computational models of DEA robots were established.The quality,speed,acceleration and other parameters of the system were calculated out.The relation between the critical breakdown voltage and the prestretching radius was obtained.Gent model is explored to derive the equation of volume and pressure combining the ideal gas law.Theoretical simulation was given to describe the change trend while a natural rubber was coupled with VHB membrane.Compared with experiments,the parameters,such as DC voltage,AC amplitudes,frequency,were analyzed,they could affect moving directions of a robot.Breakdown voltage range of natural rubbers is generally at 1.5 kV to 5.5 kV,mostly at about 2.5 kV,which relates to the thickness of rubber films.After inner rubber blast,the volume change of the DE balloon is relatively giant.Therefore,the buoyancy and acceleration of the DEA system are produced.The soft-driven robot will stay at a certain level in the sky because of the resistance from wind,pressure,etc.(5)The controllable up-and-down,rotating and translational movements of a DE actuated robot.The moving trajectory of designed flight robots was analyzed,and experimental results verified the accuracy of theoretical models.Moving directions were analyzed under the effect of DC and AC voltage.The robot can realize wireless control in rotational and translational motions,etc.A DE balloon actuator was connected to a large non-elastic chamber,the chamber was used for carrying wireless controlling system and loads.The flight acceleration was obtained by calculating volume change of the whole system.In order to realize the controlling strategy and coordinate each controller,we put forward the main controller,soft actuated controller and the tail part as independent agents.The mechanism of communication and collaboration between each part was given;The format of information exchange was developed,and the process of software designing was explained.In addition,the controllable buoyancy of a robot decreases with the increasing flight height,humidity and the decreasing temperature in the atmosphere.