A Novel Squeeze Mode Based Magnetorheological Damper:Dynamic Characteristics And Semi-active Control Strategies

Intelligent automobile is an emerging tendency featuring superior ride comfort,handling and safety,which will redefine the future transportation.The realization of “Intelligence” relies on integrated controllability,sensoring,communication and networking.The industrial trend pushes the future vehicle to be more intelligent,comfort and secure,with greater emphasis on vibration mitigation,road-holding,attitude control,as well as individualized performance demand.Semi-active suspension,a low-cost avenue handling the compromise amongst comfort,road-holding and safety,is thriving in multi-domain.Magnetorheological(MR)fluids are intelligent materials that respond to applied magnetic field and possess a compact,agile-response,energy-saving and quiet interface between electronic controls and mechanical systems,especially large force capability in squeeze mode.A novel squeeze mode based MR damper(SMRD)is proposed in this paper,with highlights of superior damping capability and low power consumption within a compact and transplantable structure.Specifically,the variable damping characteristics are optimized targeting comprehensive optimal ride,handling and safety performance;a squeeze mode based magnetorheological valve is proposed,and its structure parameters are optimized;an SMRD prototype is developed;the current-dependent damping and electromagnetic response characteristics are investigated,and a forward-feed PI current driver is developed to fulfill agile current response;model-reference sliding mode control(SMC)is implemented to compensate for the drawbacks induced by damper time delay.The structure and conclusions are organized as:1)Damping characteristics optimization.An expression featuring few parameters and unification is proposed to characterize dampers with different valve schemes.Simulation researches targeting Green Wheel 6700×CQ4 middle bus are conducted to reveal the the effects of damping characteristics on ride comfort,handling and safety performance.Degressive damping is the best option to handle the comforthandling-safety compromise,and the target damping range is obtained for the following structure optimization,with dimensionless damping coefficient 1500 for smooth road,3100 for rough road and 7000 when drivers execute handling manoeuvers.2)Structure optimization of SMRD.An optimization-oriented model of SMRD,including parameterized electromagnetic model,MR squeeze model and hydraulic model,is established.A uniform-saturation magnetic intensity principle is proposed,and a co-simulation optimal platform is developed to optimize the magnetic intensity of SMRD's dimensions.A prototype is developed and its steady-state performance is evaluated.The test results demonstrate that a pressure drop 8.5 MPa at 20 L/min and 1.0 A applied current are achieved within a transplantable and low-energy-consumption configuration.3)Dynamic characteristics of SMRD.Dynamic tests are performed to obtain SMRD's variable damping characteristics dependent on applied current.An F-PI current driver is developed to reduce the electromagnetic response time to 0.01 s.Consequently,a control-oriented SMRD's dynamic model is established.4)Time-delay dependent semi-active suspension control.A model-reference sliding mode control(SMC)is developed based on ideal linear Skyhook control.Comparative researches are performed amongst traditional semi-active control,model-reference SMC and H? optimal active control considering time delay.The simulation results demonstrate that:(1)SMC further mitigates the vibration within the sensitive frequency range(4–8 Hz),(2)SMC attains over 16% ride comfort improvement with response time delay 0–0.1 s,compared to the optimal passive suspension,(3)conventional semi-active suspension control schemes(skyhook,hybrid and ADD control,et al.)suffer from deteriorated ride performance when response time delay is over 0.03 s.This paper elaborates on SMRD's structure optimization and system integration,which oprovides efficient actuator and bottom-layer control system for semi-active suspensions.The main contributions lie in:(1)proposing and optimizing an effective magnetorheological squeeze mode based damper,utilizing MR squeeze mode and uniform-saturation magnetic intensity principle;(2)developing an efficient MR damper and an agile-response F-PI current driver,which possess large damping force capability,1.23-4.86 k N(Extension)/ 0.84-1.95 k N(Compression),and swift response of 10ms;(3)developing a time-delay dependent SMC controller for semi-active suspension,compensating for the drawbacks of time delay and achieving 16% comfort improvement.