Piezoelectric devices for vibration suppression: Modeling and application to a truss structure

For a space structure assembled from truss members, an effective way to control the structure may be to replace the regular truss elements by active members. The active members play the role of load carrying elements as well as actuators. A piezo strut, made of a stack of piezoceramics, may be an ideal active member to be integrated into a truss space structure. An electrically driven piezo strut generates a pair of forces, and is considered as a two-point actuator in contrast to a one-point actuator such as a thruster or a shaker. To achieve good structural vibration control, sensing signals compatible to the control actuators are desirable. A strain gage or a piezo film with proper signal conditioning to measure member strain or strain rate, respectively, are ideal control sensors for use with a piezo actuator. The Phase 0 CSI Evolutionary Model (CEM) at NASA Langley Research Center used cold air thrusters as actuators to control both rigid body motions and flexible body vibrations. For the Phase 1 and 2 CEM, it is proposed to use piezo struts to control the flexible modes and thrusters to control the rigid body modes. A tenbay truss structure with active piezo struts is built to study the modeling, controller designs, and experimental issues. In this paper, the tenbay structure with piezo active members is modelled using an energy method approach. Decentralized and centralized control schemes are designed and implemented, and preliminary analytical and experimental results are presented

Synthesis of Hybrid Fuzzy Logic Law for Stable Control of Magnetic Levitation System

In this paper, we present a method to design a hybrid fuzzy logic controller (FLC) for a magnetic levitation system (MLS) based on the linear feedforward control method combined with FLC. MLS has many applications in industry, transportation, but the system is strongly nonlinear and unstable at equilibrium. The fast response linear control law ensures that the ball is kept at the desired point, but does not remain stable at that point in the presence of noise or deviation from the desired position. The controller that combines linear feedforward control and FLC is designed to ensure ball stability and increase the system's fast-response when deviating from equilibrium and improve control quality. Simulation results in the presence of noise show that the proposed control law has a fast and stable effect on external noise. The advantages of the proposed controller are shown through the comparison results with conventional PID and FLC control laws

Application of the novint falcon haptic device as an actuator in real-time control

The two goals of this thesis are A) to develop an embedded system whose purpose is to control the Novint Falcon as a robot, and B) to develop a control experiment that demonstrates the use the Novint Falcon as a robotic actuator. The contents of this report are therefore divided into two parts. Part A deals specifically with the Novint Falcon, which is a PC input device which is "haptic" in the sense that it has a force feedback component. It is similar in configuration to the common delta robot, whose speed and accuracy has made it useful in pick-and-place operations. Along with its relatively low cost compared with other platforms, this makes it a good candidate for academic application in robot modeling and control. An embedded system is developed to interface with the multiple motors and sensors present in the Novint Falcon. Part B deals with demonstrating the use of the Novint Falcon as an actuator for a ball-on-plate control experiment. The results show that the device is a viable solution for high-speed actuation of small-scale mechanical systems