| Controlled nuclear fusion is one of the most ideal ways to solve the energy crisis.Among the existing technical means,Tokamak based on magnetic confinement technology is the most promising device to overcome technical difficulties of controlled thermonuclear reaction.Considering the harsh conditions（ultra-high vacuum,high temperature,and intense magnetic field）in the Tokamak vacuum chamber during maintenance state,only robotics can enter the vacuum chamber for carrying out the inspection and maintenance tasks.However,the conventional electromagnetic motors utilized by most existing maintenance robots have poor adaptability to such environmental conditions.For instance,high temperature could lead to the demagnetization of motors,high magnetic field could directly change the performance of electromagnetic motors,increasing the difficulty of the control of the systems.To overcome these issues,a novel rail-type piezoelectric robot utilizing the converse piezoelectric effect and the friction effect is proposed in this study,which serves as a carrier vehicle to implement the maintenance and overhaul tasks of the Tokamak vacuum chamber.The frame of rail-type piezoelectric robot consists of four straight beams glued with 16piezoelectric plates,two driving feet are located in the middle of two short beams.The elliptical trajectory of the driving feet will be generated by applying two AC signals with a temporal phase difference ofπ/2,and the robot is driven by friction between the driving feet and the trail.A new approach is proposed using transfer matrix method to optimize the geometry parameters and to predict the vibration performance of the proposed actuator.And the theoretical model obtained by transfer matrix method is verified by experiments.The results of the vibration experiments concur with those obtained by the calculation,verifying the accuracy of the transfer matrix model and the feasibility of the principle design.The motion experiments demonstrate the maximum mean velocity of the proposed robot achieves384.68 mm/s when the voltage is 400 Vpp.The load experiments indicated that the maximum load-weight to self-weight ratio reaches up to 7.6 at an exciting voltage of 300 Vpp,and the robot was able to withstand a horizontal pull of about 2 N at 400 Vpp.In addition,the resolution of displacement of the robot reaches 4μm under the stepping working mode,indicating that the proposed robot has good kinematics performance and load capacity. |
