ACTIVE POSITION CONTROL OF A FLEXIBLE SMART BEAM USING INTERNAL MODEL CONTROL

✍ Scribed by Y.-S. LEE; S.J. ELLIOTT

• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 511 KB
• Volume: 242
• Category: Article
• ISSN: 0022-460X
• DOI: 10.1006/jsvi.2000.3379

✦ Synopsis

The problem of controlling the position at the tip of a #exible cantilever beam to follow a command signal is considered, by using a pair of piezoelectric actuators at the clamped end. The beam is lightly damped and so the natural transient response is rather long, and also since the sensor and actuator are not collocated, the plant response is non-minimum phase. Two control strategies were investigated. The "rst involved conventional PID control in which the feedback gains were adjusted to give the fastest closed-loop response to a step input. The second control strategy was based on an internal model control (IMC) architecture. The control "lter in the IMC controller was a digital FIR device designed to minimize the expectation of the mean square tracking error. In practice, such smart beams could be exposed to temperature #uctuations and changes in geometry. The e!ect of these variations on the stability was studied and it is shown that the need for robustness to such variations leads to a limitation in the performance of an IMC controller. The improvement in the stability robustness by incorporating control e!ort weighting into the cost function being minimized was investigated, as was the incorporation of modelling delay in the design of the IMC control "lter. The IMC controller designed for the beam was found to have much reduced settling times to a step input compared with those of the PID controller while maintaining good robustness to changes in temperature. However, the extremely low damping of the experimental beam made it di$cult to implement an accurate plant model in practice.