Research On Fuzzy Control Of Helicopter Seat Suspension Buffer System Based On MREA

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%.