功率超声波换能器恒电压控制策略研究

发布时间：2018-11-08 15:02

【摘要】：功率超声波理论研究的日趋完善,使得以此为基础的多类型超声波设备得到广泛应用。相对于传统的化学粘合剂、热熔等粘合方式,超声波焊接作为一种新型焊接工艺优势明显,而且环保无污染。超声波驱动电源作为超声波焊接机中的重要组成部分,其功率调节能力和输出振幅的稳定性将直接影响焊接的质量。文章基于控制理论,开展面向热塑性材料点焊机的数控超声波电源恒振幅控制策略及仿真的主要研究工作如下:(1)针对超声波振动设备中的核心部件——换能器的非线性现象和大功率同小信号下特性变化,依据等效电路展开机理分析,并通过实验得到带负载压电换能器的输出振幅与环境温度、输入信号频率、施加电压的关系,为换能器机理建模提供现实依据。(2)针对压电换能器在工作过程中存在的迟滞、蠕变等非线性特性,将换能器中电学参数表现为受到干扰的变值,依据换能器工作中力电转换过程,建立压电换能器与换能器换能机制的等效电路模型并转化为微分方程,然后根据超声波电源中逆变、整流和功率调整模块的输入输出关系,得到整个换能机制的状态空间方程。(3)依据所建立的压电换能器的状态空间模型,提出了基于鲁棒控制理论的前馈控制算法。并结合系统模型的不确定信息,设计出符合要求的控制律,使得参数在有界扰动下能有效保持系统的性能稳定。为了避免由于模型中输入偏差的累加造成计算量过大的问题提出了基于积分分离的PID算法。为了将非线性系统通过模糊辨识后用于自适应控制,结合直接逆模型控制和迭代学习控制的思想对被控对象进行参数辨识思想,建立了基于DFS-PI的控制算法。最后,论文对数字超声波点焊机在缓变负载和突变负载条件下进行测试,超声波驱动电源振幅稳定性能达到期望,验证了所提出控制策略的有效性。
[Abstract]:With the improvement of power ultrasonic theory, the multi-type ultrasonic equipment based on it has been widely used. Compared with the traditional bonding methods such as chemical adhesive and hot melt, ultrasonic welding is a new welding technology with obvious advantages, and environmental protection and no pollution. As an important part of ultrasonic welding machine, the power regulation ability and the stability of output amplitude of ultrasonic power supply will directly affect the quality of welding. Based on the control theory, The main research work of numerical control ultrasonic power supply for thermoplastic material spot welder is as follows: (1) aiming at the nonlinear phenomenon of transducer, the key component of ultrasonic vibration equipment is discussed. The characteristic change of high power and small signal, Based on the analysis of the equivalent circuit expansion mechanism, the relationship between the output amplitude of the loaded piezoelectric transducer and the ambient temperature, input signal frequency and applied voltage is obtained through experiments. It provides a practical basis for the modeling of transducer mechanism. (2) in view of the nonlinear characteristics of piezoelectric transducer such as hysteresis, creep and so on, the electrical parameters in the transducer are represented as disturbed variable values. The equivalent circuit model of piezoelectric transducer and transducer energy transfer mechanism is established and transformed into differential equation according to the process of electro-force conversion in transducer operation. Then according to the input and output relation of inverter, rectifier and power adjustment module in ultrasonic power supply, the equivalent circuit model of piezoelectric transducer and transducer energy transfer mechanism is established and transformed into differential equation. The state space equation of the whole energy transfer mechanism is obtained. (3) based on the state space model of piezoelectric transducer, a feedforward control algorithm based on robust control theory is proposed. Combined with the uncertain information of the system model, a control law that meets the requirements is designed, so that the parameters can effectively maintain the performance stability of the system under bounded disturbance. In order to avoid the problem of excessive computation caused by the accumulation of input deviations in the model, a PID algorithm based on integral separation is proposed. In order to apply the nonlinear system to adaptive control after fuzzy identification and combining the idea of direct inverse model control and iterative learning control, the control algorithm based on DFS-PI is established. Finally, the digital ultrasonic spot welding machine is tested under the condition of slow load and sudden load. The amplitude stability performance of the ultrasonic drive power is up to expectations, and the effectiveness of the proposed control strategy is verified.
【学位授予单位】：杭州电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TP273;TB552

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