Experimental Research On Vibration Control Of Rotating Double Flexible Piezoelectric Beams With Planetary Reducer

Rotating double flexible beams structures such as space robot, solar panel on spacecraft and propeller show features, characterize light mass, low damping ratio and low stiffness. The vibration problem will influence the position accuracy of arm and the stability of the system when they are slewing or external disturbance happens. The planetary reducer connected with the flexible beam structure inevitably exist nonlinear features including friction and backlash. The double beams control system is typically a strong coupling nonlinear multiple-input multiple-output(MIMO) system, under the influence of coupling effect and nonlinear characteristic. This system is hard to control. Therefore, it is necessary to design control algorithm for this system, to suppress the vibration of the rotating double flexible beams structure.For the existence of the reducer backlash, the double flexible beams system shows the vibration characteristics mainly in the form of inverted-phase. This makes it impossible to control the system using a servo motor only. Furthermore, the nonlinear features of friction and backlash will decrease the control performance when applying model based control methods. Based on this, a traditional proportional and derivative(PD) controller was designed to control the vibration firstly. Secondly, a nonlinear T-S fuzzy control algorithm for MIMO system was studied. The controller makes full use of the decoupling design technique and sub-control strategy based on properly designed T-S fuzzy rules. Therefore, the low amplitude vibration near the equilibrium point can be fast eliminated. At last, a hierarchical fuzzy control algorithm was developed based on the MIMO system. Using this controller, the state of the controlled system can be divided into different modes by introducing a hierachical structure in fuzzy controller to achieve satisfactory performance. The hierachical structure greatly solves the problem of fuzzy rule explosion and the contradiction of completeness and compatibility of fuzzy rules.The experimental platform is designed and established. The piezoelectric sensors were used to acquire the vibration signal of double flexible beam. The piezoelectric actuators and the alternating current(AC) servo motor are used to attenuate the vibrations. The traditional PD algorithm, the designed nonlinear T-S fuzzy algorithm and the hierarchical fuzzy algorithm were used in the vibration control experimrnts. The experiments were conducted by utilizeing the following control schemes: single piezoelectric actuator control, double piezoelectric actuators control, single anti-connected piezoelectric actuator control, double anti-connected piezoelectric actuators control, AC servo motor control, double piezoelectric actuators and AC servo motor control, double piezoelectric actuators control in the process of AC servo motor rotating. The experimental results demonstrate that the investigated fuzzy methods can suppress both the large amplitude and low amplitude vibrations in a shorter time as compared to traditional PD controller. The experimental results also proved the infeasibility of control scheme with anti-connected piezoelectric actuators.