【作者】 程廷海；

【导师】 包钢；

【作者基本信息】 哈尔滨工业大学 ， 机械电子工程， 2013， 博士

【摘要】 以压缩空气为工作介质的气动技术在工业生产等领域得到了广泛应用，但是由于气体介质的可压缩性大以及非线性严重，导致气动系统的定位精度较低以及低速运动时易爬行等问题，限制了气动技术的发展。针对这一问题，本文提出了一种采用新型工作原理的螺旋式超声解锁与速度控制机构（文中命名为超声运动控制机构），将其应用到气动控制系统中，目的在于改善气动系统的定位精度与速度控制能力。通过对超声振动的减摩效应与超声驱动作用的机理分析，得出超声运动控制机构提出的理论与实验基础。超声运动控制机构主要由超声振子与螺纹输出轴组成，在超声振动的减摩效应与超声驱动的共同作用下，控制超声振子同螺纹输出轴间摩擦系数，提供二者间相对运动趋势，实现螺旋式传动副的自锁与解锁状态转换以及速度控制的功能。通过定义螺纹距径比、摩擦系数剩余率以及判定系数的概念，分析了螺纹参数与摩擦系数对超声运动控制机构的自锁与解锁状态的影响规律。分析结果表明，当判定系数大于1时，超声运动控制机构处于解锁状态；选择大的螺纹距径比，减小摩擦系数剩余率，有利于机构的解锁设计。通过建立该机构的电压-速度控制特性的数学模型，得出其具有承载能力大、输出速度线性可控的特点。考虑转动惯量与剪切变形的影响，对自由约束弯曲振动梁的共振频率计算公式进行了修正，扩展了频率计算公式的适用范围。采用有限元仿真与实验测试的方法，验证了理论分析结果的正确性。以修正公式为理论基础，建立了用于描述弯曲振动梁的固有振动特性的谐振曲线的数学模型，为开展弯曲振动模态超声振子的振动特性研究提供了理论基础。通过对压电片贴片式弯曲振动模态超声振子的布片激振方式进行分析，研究了压电元件的布片位置与布片长度对超声振子输出性能的影响规律。得出压电片的布片位置位于超声振子振动的中心波腹处，布片长度不宜超过两个振动节点间距离为合理的布片方式。采用有限元分析的方法，验证了理论分析结果的正确性，为开展柱状弯曲振动模态超声振子的设计提供了理论指导。实现了两种不同结构与激振模式的超声运动控制机构原型样机的研制。一种为行波单波长超声运动控制机构，超声振子采用黄铜材料的中空方柱型结构，自重24g，尺寸为长×宽×内径为20mm×8mm×M4mm；另一种为行波三波长超声运动控制机构，超声振子采用外表面加工有十二棱面的中空柱状多面体结构，材料为45号钢，自重206g，尺寸为长×宽×内径为36mm×46mm×Tr38mm。通过定义转折负载、稳态速度以及载重比的概念，开展了超声运动控制机构在质量负载下的实验研究。两台样机均可实现螺旋式传动机构的自锁与解锁状态转换功能。通过调节激励电压，可实现对机构输出速度的线性控制。单波长超声运动控制机构的激振频率为49.30kHz，激励电压有效值7V时，载重比为30：1以上；三波长超声运动控制机构的激振频率为42.90kHz，激励电压有效值14V时，可获得80：1以上的载重比能力。将三波长超声运动控制机构应用于气动控制系统中，实现了一套带有超声运动控制机构的新型气动控制系统，测试了该系统的定位与速度控制特性。测试结果表明，通过控制超声运动控制机构，可以完成对气动系统的位置定位与速度控制。与传统气动系统中采用机械锁紧的定位方式相比，带有超声运动控制机构的新型气动控制系统可以获得更高的定位精度；系统的输出速度与超声运动控制机构的激励电压呈线性变化，与系统回路的气体流量无关，提高了气动控制系统的抗干扰能力，特别适用于具有低速运动控制需求的场合。更多还原

【Abstract】 The pneumatic technology utilizing compressed air has an extensive applicationin industrial manufacture. Due to the high compressibility and nonlinearity ofcompressed air, the low positioning accuracy and stick-slip motion under low velocityare caused to pneumatic system. And the applications of pneumatic technology arerestricted. Aiming at this problem, a type ultrasonic unlocking and velocity controlmechanism with screw structure named ultrasonic motion control mechanism (forshort UMCM in this paper) based on novel working principle is proposed. TheUMCM is used in pneumatic system and the performance of position and velocitycontrol is to be improved.The principles of ultrasonic driving and friction reduction effect induced byultrasonic vibrations are analysed, and the foundations of UMCM conception both intheory and experiment are established. The UMCM is comprised by an ultrasonicactuator and screw output shaft. Utilizing the friction reduction effect and ultrasonicdriving, the friction coefficient between the ultrasonic actuator and screw output shaftis reduced and a movement trend between each other is produced. The screw lockingand unlocking statuses of UMCM are transformed and the velocity is controlled.The concepts of friction coefficient remainder rate, rate of screw pitch todiameter, and judging coefficient are defined. The influence of these parameters onthe statuses of locking and unlocking are discussed. It is indicated that when thejudging coefficient is over1, the unlocking status of UMCM can be gained. It is infavour of unlocking design foe UMCM by choosing the larger rate of screw pitch todiameter, and decreasing the friction coefficient remainder rate. A mathematicalmodel of voltage-velocity control characteristics for UMCM is established and thefeatures such as large bearing capacity, output velocity linear control are obtained.Considering the influence of rotary inertia and shear deformation, an amendedformula used for calculating the resonant frequency of bending vibration mode beamis deduced. The range of using for beam calculated by the amended formula isextended. The theoretical result is confirmed both by finite element simulation andexperiment method. Based on the amended formula, a mathematical model ofresonant characteristics curve used for describing the inherent characteristics ofbending beam is founded. A theoretical basis employing for the investigation ofultrasonic actuator utilizing bending vibration mode can be afforded.The exciting mode of PZT plates in plate-attached bending ultrasonic actuator isanalysed theoretically, and the influence of disposition and length of PZT plates on the ultrasonic actuator output performance are researched. The logical dispositionlocation of PZT plates is at the centre wave loop of bending vibration. And the lengthof PZT plates should not be larger than the distance between the two vibration nodes.The simulation confirmation is accomplished to theoretical results by finite elementmethod. A reference for bending ultrasonic actuator design is provided.Two prototypes of UMCM utilizing different structures and exciting modes aredeveloped. One prototype of one wavelength driving mode is adopted with a brasshollow square column structure, and has a weight of24g. The length, width and innerdiameter of this prototype are20mm,8mm, and M4mm, respectively. The otherprototype of three wavelength driving mode is adopted. The latter has a weight of206g, and a hollow steel tube structure with twelve planes is used. The length, width andinner diameter are36mm,46mm, and Tr38mm, respectively.The concepts of steady velocity, inflection load and rate of mass load to selfweight are defined, and an experimental research of UMCM under mass load iscarried out. The transform functions of locking and unlocking with screw structurecan be achieved for the two prototypes. The exciting frequency of one wavelengthUMCM is49.30kHz, and a rate of mass load to self weight is more than30:1underan exciting voltage effective value of7V can be gained. The exciting frequency ofthree wavelength UMCM is42.90kHz, and a rate of mass load to self weight is morethan80:1under an exciting voltage effective value of14V can be gained.The three wavelength UMCM is applied in pneumatic control system, and anovel pneumatic control system with UMCM is achieved. The characteristics such asposition and velocity control of this novel pneumatic control system are tested. It isindicated that the position and velocity control functions of this system can beachieved by controlling UMCM. Compared to the positioning method by mechanicallocking in traditional pneumatic system, a higher positioning accuracy can beobtained in the novel pneumatic control system. The output velocity of the novelsystem can be controlled linearly by exciting voltage, and has an independence onflow of pneumatic circuit. So, the interference immunity is improved and this novelpneumatic system can be applied specially in the occasion of low velocity control.更多还原