Abstract:Owing to high center of mass, long and heavy spray beam, the high clearance self-propelled sprayer has a tendency to swing when it runs on the bumpy farmland. Especially the frequency of the excitation from ground is approximately the inherent frequency of the suspension, which will result in reduction of work quality or even endangering security of itself. So a scheme of an active pneumatic suspension controlled in due course was put forward to address the issue. But in practical control process of the active pneumatic suspension, several problems need to be taken into account simultaneously, including the nonlinearities existed in the air spring system, requirements about multivariable control of the acceleration and displacement as well as the constrained conditions for output force or suspension distance. Aiming at above problems, a vibration control scheme of joint controller with H∞ state-feedback control and time-frequency nonlinear control was established. Firstly, the optimal gain of state-feedback controller was solved under H∞ condition with constrains. With it the appropriately objective pressure of the air spring could be computed in each moment of the control process. Then, the time-frequency controller handled a proportional solenoid valve to enable the inner pressure of air spring to meet the objective pressure. Experiments were implemented to verify the control strategy based on a test-bench of active pneumatic suspension. Under the harmonic excitation of 1.3Hz which was the first order resonance frequency of the system, the maximum sprung mass acceleration of passive pneumatic suspension was about 8.5m/s2, that of the semi-active suspension was approximately 7m/s2, whereas that of the active suspension was decreased to 2.5m/s2. In whole control process, the displacement of suspension was controlled within the limitation and reverted to initial position after impacting. Besides, responses under the condition of road random excitation were also tested. All results showed the validation of the active vibration suppressed scheme as well as the vibration control method mentioned.
