| The hydro-pneumatic suspension have been system used increasingly for variouson-road and off-road applications along with driving safety and comfort due to thehigh power density of the hydraulics and installation space. The hydro-pneumaticsuspension test system promises to simulate the dynamic responses of a heavy dutyvehicle suspension systems adapting to different terrains and speeds, validates thedesign parameters and improves reliability of the hydro-pneumatic suspension andvehicle axle in wheeled vehicles.This thesis investigates the control of a Hydro-pneumatic Suspension TestSystem developed by IEST of HIT. The development, modeling and algorithms ofpivotal control technology have been theoretically studied. The results are validatedthrough experimental activities done by a suspension bench test. The main resultsare valuable to improve the control performance and the precision of simulation.The test system constructed by a hydro-pneumatic damper and anelectro-hydraulic servo-valve controlled cylinder is modeled.The highly nonlinearcharacter of the hydro-pneumatic damper suspension system and low naturalfrequency and small damping of the loading system rre investigated. TheThree-states Control Strategy is developed for the test system, the controlparameters are designed via pole placement, which improves the dynamiccharacteristics such as extending the frequency width of system and keep the systemstable. An input filter switch between the position and acceleration signals isdesigned, and position and acceleration control schemes are implemented withoutchanging the control performance. Simulation and experimental results indicate thatthe three-state controller is effective and the method of switch control schemebetween position and acceleration controller can be achieved.The active force loading is a popular loading control method in which the forcesensor is fixed between cylinder and suspension system to measure the loading force,viscous force and inertia force. However, the disadvantage is that the controlperformance of test system may change along the stiffness fluctuation of thehydro-pneumatic damper suspension system. In common PID control，the gain ofcontroller is always low to keep system stability, thus the system characteristics arelimited. This thesis presented a variable structure controller for the highly nonlinearsystem. The therr-state control strategy including position, velocity, and acceleration information is selected as cascade function. The stability and robustness are enhancedby making use of exponential convergence. Based on the Lyapunov function, anadaptive control law is developed for the nonlinear system under parameterdisturbance and non-parametric uncertainty, which is also adopted to reduce thevibration of responses on cascade surface. Simulation results illustrate the advantageof variable structure force loading control strategy, it proposes a novel controlscheme for force loading system with states feedback.Sine signal is commonly used in control of a coordinated loading system. Whena sample is tested by multichannel at one time, the amplitude and phase of responsesignals from each channel are different. As a result, the output of test will contrary tothe expectation. This thesis introduces a control method based on single-layer&two-channel neural network to meet the requirement of an accurate recurrence control.A LMS algorithm is used to adjust the weight vector automatically and make theamplitude and phase of outputting sine signal consistent with the expected signal.Thus, the precise sine wave repetition is achieved. By analyzing the necessaryconditions for convergence of the algorithm, this thesis presents the normalizedsinusoidal recurrence control method. Advantages of this method in convergence andrapidity have been verified through the simulation and experimental analysis.Experiments on vibration test rigs in combination with time waveformreplication (TWR) can create repeatable testing conditions of the road. The objectiveof TWR is to determine the inputs to the shakers in order to obtain the same sensorreadings as during the field experiments. The classical TWR method consists of aniterative procedure that can be time consuming and divergence for a nonlinear system.This thesis presents a feedback approach based on adaptive inverse control, therebyreducing the number of iterations. By means of recursive least square (IRLS) method,a nonlinear system transfers function and its inverse function identification controllercan be designed. Experiments indicate that with the present control algorithm a betterstability can be achieved.The hydro-pneumatic suspension loading test-bed consists of a hydraulic source,a mechanical system, a hydraulic servo system and a digital control system. Based onLabView SIT (Simulation Interface Toolkit) fast control prototype technology, thedigital control software is developed to carry out the proposed control strategy.Experiments indicate that the present control schemes are effective and advanced. |
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