【作者】 刘静；

【导师】 浮洁；

【作者基本信息】 重庆大学 ， 仪器科学与技术， 2021， 硕士

【摘要】 直升机坠毁或硬着陆等意外事故时产生的冲击载荷大、时间短、能量高,对直升机机体及机上设备会造成巨大破坏,严重时甚至会威胁乘员的生命安全。传统被动式缓冲座椅悬架参数固定不可调,对不同的乘员质量、冲击速度不具有自适应性。基于磁流变材料的智能缓冲装置的阻尼力可以通过外加磁场实时调控,且响应迅速,为智能缓冲领域提供了新的手段。实现对磁流变耗能(Magnetorheological Energy Absorber,以下简称为MREA)的最佳控制以减少冲击载荷对人体的伤害至关重要。冲击过程充分利用MREA的冲程可以保证最大耗能的前提下降低冲击载荷对人体的伤害,实现“软着陆”。而如何合理的控制耗能器阻尼力的动态响应过程,使传递到人体的力峰值尽可能小于人体伤害限制是控制的难点。考虑到人体在高速下存在强非线性及瞬态性,精确的人体动力学模型能够给控制算法的设计及优化提供有效的参考。基于以上分析,本文建立了两个不同生物动力学模型,对直升机座椅悬架半主动缓冲系统的动力学响应特性和控制方法问题展开了研究,具体从以下几个方面进行研究:(1)首先建立了结合MREA的单自由度刚性乘员动力学模型(The RigidOccupant Model),分析了不同参数下的系统冲击响应特性。根据系统的响应特性及MREA的工作原理,以“软着陆”为控制目标设计了模糊控制器,在不同冲击速度下进行缓冲控制仿真,基于人体伤害评估标准与恒定载荷控制、恒定磁控力控制这两种控制器的缓冲效果进行对比。结果表明在2-12m/s冲击速度下,模糊控制器拟合的阻尼力-位移曲线实现了“平台效应”,不仅能将人体冲击响应控制在极限载荷14.5g以下,还能有效避免二次反弹。(2)考虑到实际人体为复杂的非线性系统,其对MREA的反作用会影响缓冲系统的控制效果,而单自由度模型无法准确模拟人体响应,继而提出针对第50%男性建立的多自由度非线性生物动力学模型(The Compliant-Occupant Model),建立了直升机磁流变座椅悬架系统数学模型。根据系统冲击响应特性,设计了半主动模糊控制算法。基于伤害评估标准对所设计的模糊控制器进行仿真验证,结果表明模糊控制器可有效避免二次反弹。(3)由于传统模糊控制器冲击前期控制力较大,会加剧传递到人体冲击载荷。结合恒定磁控力前期控制缓和能有效抑制冲击峰和模糊控制器能有效避免二次反弹的优点,提出可切换模糊控制器。以最小化骨盆加速度为目标,采用遗传算法搜索冲击载荷下可切换模糊控制器的切换时间及控制器最优参数以减少损伤的发生。仿真结果表明,在6m/s-12m/s的冲击速度下,相比于恒定载荷控制、恒定磁控力控制这两种控制策略,可切换模糊控制器在高速冲击下仍能将人体响应最大化地降至安全线内。(4)为了验证模糊控制的可行性和有效性,基于单自由度座椅悬架缓冲系统在冲击载荷下的控制方法的研究,在现有实验条件下建立了座椅悬架缓冲实验系统,实验结果表明,在不同的冲击激励下,模糊控制器具有明显的缓冲效果,加速度峰值最高衰减率可达30%以上。更多还原

【Abstract】 Helicopter crashes or hard landing will cause huge damage to the helicopter and equipment,and even endanger the lives of the occupants in severe cases due to the large impact load,the short impact time,and the high impact energy.But the traditional passive cushioning seat suspension is not adaptable to different occupant masses and impact speeds due to fixed and non-adjustable parameters.The intelligent buffer device based on magnetorheological materials can control the damping force in real time through an external magnetic field and respond quickly,which provides a new means for the field of intelligent buffering.It is very important to achieve the best control of Magnetorheological Energy absorber(MREA)in order to reduce the impact load to the human body.Making full use of MREA’s stroke in the impact process can reduce the impact of the impact load on the human body under the premise of maximum energy consumption,and achieve a "soft landing".In the process of "soft landing",how to reasonably control the dynamic response process of the impact force and make the impact peak as small as possible than the human injury limit is a difficult problem of buffer control.Taking into account the strong nonlinearity and transient of the human body under high-speed impact,the accurate human body dynamic model can provide an effective reference for the design and optimization of the control algorithm.Based on the above analysis,this thesis established two different biodynamic models to study the dynamic response characteristics and control methods of the semi-active cushioning system of a helicopter seat suspension,specifically from the following aspects:(1)Firstly,a single degree of freedom rigid occupant dynamic model combined with MREA is established,and the shock response characteristics of the system under different parameters are analyzed.According to the response characteristics of the system and the working principle of MREA,a fuzzy controller is designed with "soft landing" as the control target,and the buffer control simulation is carried out under different impact speeds.Based on the human injury assessment standard,the buffer effect of the fuzzy controller is compared with the constant total force controller and the constant yield stress controller.The results show that at 2-12m/s,the damping force-displacement curve fitted by the fuzzy controller achieves a "platform effect",which can not only control the impact response of the human body below the limit load of 14.5g,but also effectively avoid secondary rebound.(2)Considering that the human body is a complex nonlinear system,its reaction to MREA will affect the control effect of the buffer system,and the single degree of freedom model cannot accurately simulate the human body response.Therefore,a multi-degreeof-freedom nonlinear biodynamic model(The Compliant-Occupant Model)established for the 50%th male was proposed,and a mathematical model of the helicopter magnetorheological seat suspension system was established.According to the impact response characteristics of the system,a semi-active fuzzy control algorithm is designed.Based on the damage evaluation criteria,the designed fuzzy controller is simulated and verified,and the results show that the fuzzy controller can effectively avoid the secondary rebound.(3)Because the traditional fuzzy controller has the problem that the greater control in the early stage of impact will aggravate the impact load transmitted to the human body.Combining the advantages of the constant magnetic control force early control mitigation can effectively suppress the impact peak and the fuzzy controller can effectively avoid the secondary rebound,a switchable fuzzy controller is proposed.With the goal of minimizing pelvic acceleration,genetic algorithm is used to search the switching time of the switchable fuzzy controller and the optimal parameters of the controller under impact load to reduce the occurrence of damage.The simulation results show that at an impact velocity of 6m/s-12m/s,compared to the constant total force controller and constant yeild stress controller,the switchable fuzzy controller can still maximize the response of the human body to the safety limit even at high impact speeds.(4)In order to verify the feasibility and effectiveness of the control strategy,based on the study of the control method of the 1DOF magnetorheological seat suspension cushioning control system under impact load,the seat suspension cushioning experimental system was established under the existing experimental conditions.The experimental results show that under different shock excitations,the fuzzy controller has obvious buffering effect,and the peak acceleration attenuation rate can reach more than 30%.更多还原