【作者】 白洋；

【导师】 郭吉丰；

【作者基本信息】 浙江大学 ， 电气工程， 2013， 博士

【摘要】 多自由度超声波电机具有结构简单易装配、机械集成度高,而且驱动便捷、分辨率高,能够实现运动的多样化且不受电磁干扰等优点,可应用于机器人关节、精密装配、微小型机器人、医疗辅助设备等机电装置中,成为近些年超声波电机研究领域的热点课题。其中,具有旋转和平动两种自由度的超声波电机,因其运动方式是实际生活中常见的形式,具有较高的研究价值和广泛的应用前景。这种电机通常可以分别实现旋转和直线运动,有些电机可以实现螺栓运动。为此,本文设计了一种新型单定子旋转—直线二自由度超声波电机,并针对该电机进行了原理分析、数学建模、有限元仿真、性能测试及结构优化等一系列研究,取得的进展有：(1)提出了一种基于单定子的旋转—直线二自由度杆式超声波电机结构。该结构巧妙地利用了倾斜放置的压电陶瓷片,激发了定子弹性体两个模态的运动并将其放大为转子的宏观运动。电机仅需单电源供电,具有结构简单紧凑的特点,可以适用于微型化应用的场合。实验研制的样机最小长度仅为25mm、直径仅为2.5mm。(2)提出了一种应用于新型二自由度超声波电机的驱动方法。由于电机结构特殊,一些传统超声波电机的驱动方法不能适用。本文采用非对称方波电压输入,利用近谐振点惯性冲击的方式有效地驱动了转子运动,并通过控制输入方波的频率、占空比和幅值,分别实现了转子运动模式的切换、运动方向的改变和运动速度的调节。(3)提出了一种基于复损耗的旋转—直线二自由度超声波电机定子建模方法。本文采用等效模型推导了定子模态振型的解析解,并准确的预测了电机的谐振频率。进一步地,本文利用压电损耗因子和金属损耗因子,推导了定子端面谐振振幅的近似计算方法,用于计算在直线和旋转模式下定子端面的最大位移值和最大旋转角度。通过建立有限元模型做比对发现,数学模型计算值与仿真结果数据基本吻合,这验证了数学模型的正确性。(4)提出了一种应用于新型二自由度超声波电机的定子优化设计方法。提出以电机定子结构参数为变量,以两自由度电机定子的输出性能为优化目标,借助相对敏感系数的概念对定子进行优化设计的方案。在综合比较后,选择了多组结构建立数学模型,并研制样机。实验发现优化后的样机性能得到了大幅度提升。本研究设计的新型旋转—直线二自由度超声波电机,丰富了多自由度超声波电机的种类、延伸了其应用领域,所采用的建模和优化方法对于超声波电机的机理特性分析、结构的设计及优化有着积极的作用。更多还原

【Abstract】 Multi-degree of freedom (MDOF) ultrasonic motor (USM) has the advantages of simple structure, easy assembly, and high mechanical integration. It is also convenient to drive and able to achieve the diversification of movement. Like all the other types of USM, MDOF USM can provide high resolution motion and avoid electromagnetic interference. Now it is widely used in the industry, such as joint of the robot, precision assembly, micro robot, medical apparatus and instruments, which makes it a hot topic in the field of USM research. Among all the MDOF USMs, the rotary-linear USM has high research value and broad application prospects, as its motion is a common form in real life. This type of USM can realize rotary and linear motion, respectively, while some can realize both. In this research, a new rotary-linear bar type USM based on one single stator was developed. Its working principle, mathematical model, finite element simulation, performance testing and structural optimization were reported. The main achievements are as follows.(1) A new rotary-linear2-DOF motor structure based on one single stator was introduced. By taking advantage of the slanted ceramics, two mode of stator motion can be derived. Those microscopic motion of stator can be converted into the macroscopic motion of rotor. The motor has a compact structure and needs only one single power source, which make it well qualified in miniaturized applications. The prototype motor had only25mm length and2.5mm diameter.(2) A driving methodology applied to the new motor was proposed. As the traditional USM driving method can not be applied due to its special structure, an asymmetric square-wave type voltage is used to drive the motor. The movement of the rotor can be derived by means of smooth impact drive method (SIDM) near the resonance frequency. By controlling the driving frequency, the mode of the rotor movement can be switched. Besides, the direction and speed of the rotor movement can be adjusted by changing the duty cycle and amplitude of the input voltage, respectively.(3) A modeling method based on complex losses was developed. An equivalent model on the modal analysis was build up to calculate the nature frequencies of the stator. Further, the piezoelectric loss factor and metal loss factor were used to deduce the harmonic amplitude of the stator end. So a mathematical model, which can calculate the maximum linear displacement and rotary angle approximately, was derived. A good match was found by comparing the results from the finite element model and mathematical model, which validated the correctness of the mathematical model.(4) An optimization method applied to the new motor was introduced. The proposed mothed aimed at optimizing the output character of the2-DOF stator, by adjusting the structural parameters. The concept of relative sensitivity coefficient was utilized in the comprehensive comparison. Several groups of the motor parameters were chosen. And according to those chosen parameters, the prototype motors were made. It was found that, the performance of the optimized motor has been improved significantly.This study proposed a new rotary-linear USM, which extended the application field of MDOF motors. The modeling and optimization method will play an active role in the characteristic analysis, structure design and optimization of ultrasonic motors.更多还原