【作者】 杨莉；

【导师】 金振林；

【作者基本信息】 燕山大学 ， 机械制造及其自动化， 2014， 博士

【摘要】 基于伺服电机驱动的数控技术已广泛用于现代制造行业，并已成为核心技术，其用于成形制造领域也成为必然趋势。由于成形过程中的载荷大、成形工序种类多，伺服驱动技术至今还未能广泛地用于成形制造领域。将伺服驱动技术应用于拉深过程的压边力控制，可根据冲压工艺的特点和工艺需要，使压边力随行程变化，达到最优的控制目标。新的压边力控制技术将对冲压成形的自动化、柔性化和智能化产生积极的推动作用。这也体现了更精、更快、更省的成形理念，是先进冲压成形技术的发展趋势。本文提出了伺服驱动压边力控制方法，将伺服电机与六杆机构复合，作为控制系统的动力和机械系统的主要组成部分，设计研制了新的压边力控制系统。对该控制系统的基本原理和方法、控制系统中的机械系统和数控系统的参数优化、软件开发和控制过程的实现等关键技术，以及相关的工艺理论问题进行了研究。首先在平面应力假设条件下，对轴对称拉深成形问题，采用能量原理导出了法兰区起皱临界压边力的计算式，绘制了临界压边力随拉深过程变化曲线。采用有限元模拟方法和分别采用平面应力假设、平面应变假设以及等效应变与质点位置半径成反比三种假设条件下的理论分析方法，分析了法兰区的应变分布情况，验证了平面应力假设条件下的分析结果与实际情况更接近。然后，采用复合伺服驱动设计方案，设计了应用于正装模具结构的双滑块六杆机构的压边力执行机构。分析给出了六杆机构的运动方程，以额定工作行程内传动比、机构传动角等为约束条件，以机构总体尺寸最小为优化目标，优化确定了杆系尺寸。采用虚拟样机技术对压边系统进行了仿真分析。分别在恒定压边力和变压边力情况下，验证了复合伺服驱动方法的可行性，通过调整电机速度，实现了变压边力加载控制。分析表明，采用复合伺服驱动设计方法，产生200kN的压边力只需不超过2kW功率的电机。还分析了杆系尺寸加工误差对压料板运动精度的影响，并给出了杆件尺寸公差选择方法，为压边机构的设计提供了依据。对倒装模具结构，采用双滑块六杆机构与伺服电机复合的设计方案，综合考虑了伺服跟随系统的刚性位移和弹性位移对输出速度的影响，建立了压边力执行机构的输入与输出关系的数学模型。以伺服跟随机构中的压料板的速度与给定的压力机滑块速度之差最小及机构尺寸最紧凑为优化目标，在保证工作行程和最优传力效果的条件下，按某拉深工艺给定的压边力与滑块位移关系曲线，优化确定了机构参数。对压边过程进行了仿真分析，结果表明，当电机按预先设定的输入速度运动时，输出的压边力达到了预定的要求。输入的压边力曲线和输出压边力曲线非常接近，压边力最大相对误差小于4.7%(压边力>100kN时)。仿真分析表明，当最大压边力为194kN时，所需电机的最大转矩为36.6N×m，中小功率的电机即可满足要求。分析结果表明，采用六杆机构与伺服电机复合的设计方法，实现拉深过程的变压边力控制是可行的。进而根据数控系统的结构特点和压边力控制的总体要求，设计了压边力数控系统的硬件系统。选用伺服电机和运动控制器为系统的主要部件，根据控制系统功能的要求，设计开发了相应的软件。对压边力控制系统的伺服驱动系统、机械系统进行建模，采用Simulink进行了仿真试验。结果表明，系统具有良好的稳定性和动态性能。最后，设计研制了伺服驱动压边力控制的机械系统和数控系统，分别实现了用于正装模具结构的恒定压边力和变压边力加载。实验结果表明，采用伺服驱动压边力控制方法，可以达到工艺设定的压边力要求。实验结果还显示，在施加大约200kN压边力的情况下，电机的转矩、功率等都小于其额定值。更多还原

【Abstract】 CNC technology based on servo drive has been widely used in manufacturingindustry, and has become the core technology of modern manufacturing. Its application informing manufacturing field is going to be an inevitable trend. Due to heavy loads,diversities of processes and other difficulties in metal forming, servo drive technology isstill not widely used in forming manufacturing. By applying the servo drive technology inblank holder force control during deep drawing process, the BHF can be changed alongwith the stroke of arbitrary in order to reach the optimal control goal, according to thecharacteristics of sheet metal forming and the process requirements. This new blankholding force control technology will play an important role in promoting the automation,flexibility and intelligence of the sheet metal forming. It also reflects the advancedforming concept which is more precise, faster and more economical, presenting thedevelopment tendency of the advanced stamping technology.This paper presents a servo drive blank holding force control method whichcomposes a servo motor and a six-bar mechanism acting as the power of the controlsystem and the main part of the mechanical system and a new BHF control system isdeveloped. Researches on the basic principles, optimizations of the mechanical systemand the numerical control system, the designs of the hardware and software of the controlsystem and the related processing theories were made.First, the formula of critical BHF of flange region in axisymmetric deep drawing isdeduced under the plane strain assumption and the energy principle. Meanwhile, thevariation curve of the BHF versus the travel distance changing is drawn. Comparisonsunder the assumptions of plane stress, plane strain and equivalent strain inverselyproportional to radial coordinates in the flange region is made and results show that theplane stress condition is the closest to the actual situation.Then, taking an upright constructive mold for instance, the BHF actuator withdouble-slider and six-bar mechanism is designed adopting the composite servo drivemethod. The analysis gets the motion equation of the six-bar mechanism which can optimize linkage sizes under constraint conditions such as the drive ratio in the ratedworking stroke and the drive angle, and the goal is to optimize the overall size.Simulations of the blank holding system by virtual prototype technology are taken underthe circumstances of the constant BHF and the variable BHF. And the feasibility of thecomposite servo drive method is proved under the variable BHF by adjusting the motorspeed. The analysis indicates that it only requires motors below2kW to generate200kNBHF adopting the new drive method. In addition, how the linkage size machining errorsinfluence the precise movement of blank holders are analyzed. A linkage size toleranceselecting method is proposed as a basis to design blank holding mechanisms.For inverted pattern structures, a mathematical model indicating the input and outputof the BHF actuator is established, adopting the composite drive method, and consideringhow the rigid and flexible distances effect on outcome speeds. In order to minimize thedifference value between the binder speed and the sliding block speed, mechanismparameters are determined based on the BHF-slide distance curve from a deep-drawingprocess, under the conditions of guaranteeing the working stroke and the optimum valueof loading-pass effects. The simulation of blank holding process proves that the outputsmeet the requirements when the input motor speed is given. The input BHF curve and theoutput BHF curve are very close to each other. And the minimum relative error is lessthan4.7%when the BHF is more than100kN. It also indicates that the maximum torqueis36.6N×m when the max BHF is194kN, in other words, small or medium-sized powermotors can meet the requirements. The analysis results show that the variable BHFcontrol adopting composite method combining the six-bar linkage drive technique andthe servo motor drive technique is feasible.Furthermore, according to the characteristics of numerical system structures and therequirements of the BHF control, the hardware of the numerical BHF control system isdesigned. The system mainly consist servo motor and motion card. And the relatedsoftware is developed according to the requirements of the control system. Models of theservo drive system and the mechanical system are built and simulations are carried out byusing Simulink. It’s shown that the system has good feasibility and good dynamicproperty. Finally, the mechanical system and the numerical control system under the controlof the servo drive BHF are designed realizing the constant BHF and the variable BHFloading for upright constructive molds. The experimental results indicate thattechnological BHF requirements are reached adopting the BHF control method of theservo drive. Torque and power of motors are lower than rated values under thecircumstance that the blank holding force is up to about200kN.更多还原