高强度大刚度高可靠结构化超定飞机起落架的动力学分析与轻量设计

The resistance from a landing gear system covers half of that of the whole airplane. Therefore, most of the landing gears are often designed to be retractable in mechanism. But the accidents resulting from the landing gear systems have covered more than 60% of the total accidents ever since 1942. The dead point configuration of a four-bar mechanism within which there are two collinear links is the common bearing form of structure in the existing landing gear systems. This ideal configuration geometry of landing gear mechanism is very difficult to maintain stably in reality. The guidance mechanism of a landing gear system is also the bearing structure which renders the successive failures and the final fracture of the whole landing gear when any functional structure in the system failed to work. This proposal was planning to use the analytical theory of degree of freedom of mechanisms to fulfill the innovative design of a redundantly constrained landing gear mechanism so that the functions of drive, lock and load bearing are accomplished by independent structures. In accordance to the synthesis of redundant constraints, the inner stresses of any links or part are decreased ultimately, and therefore the requirement for the material is also reduced while the structural strength and stiffness are enhanced. According to the independent functional design philosophy, the successive failures are avoided from the structure and as a result the systematic reliability is improved. By setting the redundant actuators, the deploying and retracting motions of the landing gear system is effectively safeguarded. All These procedures further promote the reliability and working life of the whole landing gear system and form the synthesis theory and method for redundantly constrained mechanism of landing gear system with high strength, high stiffness and high reliability.

飞机高速飞行时起落架产生的阻力接近整机阻力的一半，因此，起落架大都设计成可收放式。利用四杆机构的死点位置而组成两构件共线的承载结构是当前可收放起落架的基本形式，但自1942年以来起落架导致的事故已超过总事故的60%。这说明在工作中很难始终保证这一理想的共线条件。而导引机构同时也是承载结构的设计使得任意功能结构的失效都会导致起落架整体级联失效直至破坏。本项目拟运用机构自由度解析理论，通过对机构运动和约束的综合，实现结构化超定起落架的源头创新，达到驱动、锁止和承载功能的独立。根据结构的超定综合，从承载上降低任一结构件的内应力，降低对材料的要求，提高起落架的结构强度和刚度；利用功能的独立设计，从结构上切断失效的级联传递，提高系统的可靠性；通过驱动的冗余配置，从执行上确保起落架收放的稳定性，进一步提高起落架的系统可靠性和使用寿命，获得具有高强度起落架的结构化超定机构综合理论与设计方法。

飞机高速飞行时起落架产生的阻力接近整机阻力的一半，因此，起落架大都设计成可收放式。利用四杆机构的死点位置而组成两构件共线的承载结构是当前可收放起落架的基本形式，但自1942年以来起落架导致的事故已超过总事故的60%。这说明在工作中很难始终保证这一理想的共线条件。而导引机构同时也是承载结构的设计使得任意功能结构的失效都会导致起落架整体级联失效直至破坏。本项目通过对机构运动和约束的综合，实现了结构化超定起落架的创新设计。在理论分析方面，通过对运动和约束的分析，探索了结构强度、刚度和紧凑性方面的基本问题；综合出了具有完全折叠功能的轻量化飞机起落架，实现了驱动、锁止和承载功能的独立性分配。在机构静力学分析的基础上，研究了机构约束的综合。当其完全放下并锁止在工作状态后形成结构化超定的桁架结构，最大限度地降低承载结构的工作内应力。在结构综合方面，根据起落架的超静定设计要求，从承载上降低任一结构件的内应力，提高起落架的结构强度和刚度，将过约束引入到起落架结构设计中，综合出高强度、大刚度的结构化超定起落架机构。在超静定高强度起落架结构创新设计方面，依据功能独立设计理念，综合出了具有垂直收放功能的过约束起落架。当完全放下起落架时形成超静定自锁的桁架结构，具有高强度和高承载能力。锁止机构实现起落架的姿态保持功能，在飞机降落时并不承担主要载荷。对称布置冗余驱动系统，大幅提高驱动系统可靠性，降低了驱动系统失效概率。在起落架系统多刚柔动力学建模和刚度优化方面，研究了飞机起降过程中起落架的动力学和载荷传递特性。运用牛顿-欧拉方程研究了系统的动力学响应，实现了结构化超定机构的系统动力学分析。在起落架典型零部件制造工艺研究方面，考虑到这些典型零部件的自重和空气阻力，分析了起落架关键零部件结构特征和装配要求，得到了起落架零部件制造工艺参数与装配应力和形变的映射关系，并分析制定了合理的制造工艺参数和流程。