Kougen Ma

Vibration control of smart structures with bonded PZT patches: novel adaptive filtering algorithm and hybrid control scheme

This paper focuses on a novel adaptive filtering algorithm, hybrid adaptive control scheme and their application to real-time vibration control of smart structures. A novel adaptive filtering algorithm is presented and compared with the least mean square algorithm, showing a faster convergence rate, better noise-smoothing capability and wider search field. A hybrid adaptive control scheme is then proposed and analyzed. The scheme takes advantage of both feedback control and feedforward control and provides the high damping, fast vibration suppression, good robustness and easy realization due to small computation complexity. The novel adaptive filtering algorithm and the hybrid control scheme are verified on a cantilever beam with four bonded PZT patches. Satisfactory vibration reduction has been observed for both single-input and single-output, and multi-input and multi-output, control cases under sinusoidal, swept frequency sinusoidal and random disturbances, confirming the reliability and validity of the novel adaptive filtering algorithm and the hybrid adaptive control scheme.

Frequency-weighted adaptive control for simultaneous precision positioning and vibration suppression of smart structures

This paper focuses on a frequency-weighted hybrid adaptive control with application to simultaneous precision positioning and vibration suppression of smart composite structures. Following the introduction of the structure and materials system of an active composite panel (ACP) with a surface-mounted and two embedded piezoelectric ceramic patches, the sensor selection for the purpose of precision positioning or vibration control is discussed, and the function assignment of a laser displacement sensor as well as the embedded piezoelectric sensor is determined for the ACP. The frequency-weighted hybrid adaptive control approach is then developed. The approach consists of an adaptive feedforward position controller for precision positioning, an adaptive feedforward vibration controller for vibration suppression as well as an adaptive feedback controller for both precision positioning and vibration suppression. The frequency-weighted filters introduced in the approach realize the signal fusion of the two sensors. Finally, experiments are also performed for harmonic disturbances at the first two natural frequencies of the ACP and a random disturbance for both cases of with/without the adaptive feedforward vibration controller, demonstrating that the frequency-weighted hybrid adaptive control approach can provide satisfactory precision positioning and vibration suppression in both cases, and that better position accuracy can be achieved if the adaptive feedforward vibration controller is also employed.

Adaptive Simultaneous Precision Positioning and Vibration Control of Intelligent Composite Structures

This paper presents an adaptive control scheme for simultaneous precision positioning and vibration suppression of intelligent structures. First, the structure and materials system of an active composite panel with piezoelectric ceramic patches are introduced. An adaptive control scheme, which consists of an adaptive feedback and two adaptive feedforward controllers, is then proposed. The two adaptive feedforward controllers are responsible, one for precision positioning and the other for vibration suppression, and the adaptive feedback controller affects both precision positioning and vibration suppression. Two PID feedback controllers and the proposed adaptive control scheme are experimentally studied on the active composite panel under harmonic and random disturbances, demonstrating that (a) for the PID feedback control, the controller gains should be chosen carefully to make a tradeoff between position tracking and vibration suppression, and the positioning accuracy varies for different disturbances due to residual vibrations; and (b) for the proposed adaptive control scheme, the vibration is entirely suppressed and the positioning accuracy is consistently excellent no matter what kind of disturbance is encountered, the relative steady state error is 3%, and the controller can adjust its weights to adapt to the changes of the command and the external disturbances.

Adaptive Control of Flexible Active Composite Manipulators Driven by Piezoelectric Patches and Active Struts With Dead Zones

Simultaneous adaptive positioning and vibration control of a flexible active composite manipulator with two piezoelectric patches and an active strut are investigated in this paper. First, the configuration of the manipulator is described, and then its dynamics is analyzed. An adaptive fuzzy logic control (AFLC) strategy and an independent modal space adaptive control (IMSAC) scheme are proposed for the active strut motion control and for the manipulator vibration control, respectively. In the AFLC, an adaptive input scaling concept is introduced to adaptively adjust the input of a traditional fuzzy logic controller. As a result, an inverse dead zone is gained to compensate the existing strut dead zone and overcome the dead zone effects. In the IMSAC, a novel adaptive feedback control scheme is developed using the adaptive filtered-x algorithm that is commonly used for adaptive feedforward control. Simulations and experiments demonstrate that the AFLC can provide very accurate positioning control with a relative steady-state positioning error of 0.06%, and that the IMSAC raises the damping ratios of the first two modes of the flexible manipulator 10 times and substantially suppresses the vibration induced by the manipulator motion.

Adaptive input shaping and control for simultaneous precision positioning and vibration suppression of smart composite plates

This paper focuses on simultaneous precision positioning and vibration suppression of smart composite plates with multiple piezoelectric patch actuators. Following the analysis, measurement, and estimation of a smart composite plate dynamics is the development of a multi-reference and multi-channel adaptive algorithm and an adaptive control strategy. The introduced adaptive control strategy consists of an adaptive input shaping unit and an adaptive positioning/vibration control unit, and both units are designed by applying the adaptive algorithm. The adaptive input shaping unit is used to suppress free vibration due to the smart composite plate motion and to expedite the convergence of the adaptation of the adaptive positioning/vibration controller. The adaptive positioning/vibration controller then provides precision positioning control and reduces the vibration due to the motion of the plate and/or external disturbances. In addition, an internal model configuration is employed to provide the reference needed in the adaptive control strategy and the effect of the discrepancy between the estimated dynamic model and the plate on the performance of the controller is also explored. The experiments demonstrate that the adaptive control strategy has excellent capabilities of positioning and vibration controls for various positioning and vibration conditions of the smart composite plate.

Finite Element Charts and Active Vibration Suppression Schemes for Smart Structures Design

This article employs a finite element method to introduce Displacement-Load-Sensor voltage-Actuator voltage (DLSA) Design Charts and associated vibration suppression schemes; namely, Constant Voltage (CV), Optimum Voltage (OV), Corresponding Voltage (COV), and Truncated Corresponding Voltage (TCOV), to develop actuator control voltages with amplitude and phase information for the design of smart structures with piezoelectric sensors and actuators for active vibration suppression. These techniques can be used to (a) design the location, size, and number of actuators without resorting to complex control strategies or formal optimization techniques, (b) investigate the actuation effectiveness of surface-mounted versus embedded piezoelectric patches in similar composite structures, and (c) determine actuator control voltages analogous to a feedforward open-loop control technique. Guidelines are presented for the development of DLSA Design Charts. In addition, closed form analytical equations that can replace DLSA Design Charts, are developed and presented due to their ease of use. An Active Composite Panel (ACP) with a surface-mounted piezoelectric patch actuator for lateral vibration suppression and an Active Composite Strut (ACS) with a piezoelectric stack actuator for axial vibration suppression are considered. The ACP and ACS are employed to demonstrate the applications of the introduced DLSA Design Charts and the vibration suppression schemes for vibration suppression and actuator placement optimization. The vibration suppression of both ACP and ACS is significant over a frequency range encompassing several resonances, and is indicated by the Suppressed Vibration Energy (SVE) index. This investigation shows that the optimum location of the actuator depends on the structural mode shape, based on the criteria of maximum SVE and minimum actuator power. In general, the actuator should be placed on the panel on a sub-area, where the sum of normal strains is maximum. However, a preferred location can be determined over a range of frequencies that encompass more than one natural frequency.

A finite element analysis approach with integrated PID control for simultaneous precision positioning and vibration suppression of smart structures

This paper focuses on the development of an ANSYS finite element analysis (FEA) environment with integrated PID control scheme for simultaneous precision positioning and vibration suppression of smart composite structures with piezoelectric flat patches acting as actuators. This environment includes three modules: structural modeling, PID controller design, and dynamic analysis of smart structures. Two types of PID controllers are investigated, namely, PID vibration suppression (PID-VS) controller and PID simultaneous precision positioning and vibration suppression (PIDSPPVS) controller. The PID-VS controller is suitable to perform only vibration suppression with no positioning capability. The PID-SPPVS controller is equipped with SPPVS capabilities. The characteristics of individual control gains and their behavior with respect to each other for the two PID controllers are also studied. The gain selection for the PID-VS controller is based on obtaining the best VS while the gain selection for the PID-SPPVS controller is based on achieving the best positioning accuracy and VS simultaneously. In this study, a horizontal cantilevered graphite/epoxy composite beam with one surface-mounted ACX piezoelectric flat patch located at the beam root is first modeled. Next, the FE modal analysis is performed to determine the natural frequencies and hence the time step interval needed for the FE transient analysis. During the transient analysis, the mid-point of the beam tip is subjected to different types of external excitations such as sine loadings with different frequencies as well as random forces to evaluate the two PID controller performances. It is demonstrated that the FEA model with integrated PID-SPPVS controller is able to reach the desired position in a much shorter time in comparison to the PID-VS controller. Vibration amplitude reduction capabilities for the both PID controllers are very similar, although the PID-VS controller performs slightly better. This study also implies that the integrated FEA environment, consisting of the structural modeling of active composite structures with piezoelectric flat patches, modal and transient analyses, controller design, and simulation, provides a powerful tool for the design, analysis, and control of smart structures with SPPVS capabilities.

Hybrid adaptive control of intelligent structures with simultaneous precision positioning and vibration suppression

This paper focuses on the dynamic analysis, simultaneous precision positioning and vibration suppression, and experiments of Active Composite Panels (ACPs). First, the dynamics of a panel with two surface-mounted PZT patches is analyzed and measured by the finite element method and experiments. A hybrid adaptive control scheme is then proposed to achieve precision positioning and vibration suppression simultaneously. The control scheme takes advantage of two adaptive feed forward controllers and an adaptive feedback controller. The simulation results of the hybrid adaptive controller are compared with those of a PID controller, showing that it can provide better precision position and faster vibration suppression. The experimental results demonstrate that the relative precision can reach 98.5% of the required position in large vibration level, verifying that the hybrid adaptive control scheme is reliable and efficient.

Integration, control, and applications of multifunctional linear actuators

The integration, analysis, control, and application of a linear actuator are investigated. The linear actuator has super-precision, large stroke, and simultaneous precision positioning and vibration suppression capabilities. It is an integration of advanced electro-mechanical technology, smart materials technology, sensing technology, and control technology. Based on the electromechanical technology, a DC-motor driven leading screw ensures the large stroke of motion and coarse positioning. The smart piezoelectric technology makes the fine positioning and vibration suppression over a wide frequency range possible. The advanced control strategy greatly compensates the hysteresis characteristics such as backlash and/or dead zone, and enables the excellent performance of the actuator. Several sensors such as load cells, displacement sensors, and encoders are also integrated for various applications. Controller design and testing of this linear actuator are also conducted. The applications of the linear actuator are also explored in precision positioning and vibration suppression of a flexible manipulator and smart composite platform for thrust vector control of satellites.

Adaptive internal model control for simultaneous precision positioning and vibration suppression of smart structures

This paper focuses on adaptive internal model control of smart structures with simultaneous precision positioning and vibration suppression functions. First, the structure, manufacturing, and test of an Active Composite Panel (ACP) with surface-mounted piezoelectric ceramic patches are introduced. Based on the discussion of the 2-DOF internal model control scheme, an adaptive internal model control scheme is then presented, in which the controller is constructed in form of a finite impulse filter, and the filtred-x LMS algorithm is employed to adapt the coefficients of the filter. Finally, the adaptive internal model control scheme is experimentally verified on the ACP, and compared with the adaptive feedforward control scheme, showing that it can produce more accuracy and faster response process. The satisfactory performance confirms that the adaptive internal model control schem is reliable and efficient.