Large-scale robotic manipulators are used in diverse engineering fields such as aerospace, automotive and heavy industries. These manipulators are considerably heavy and sluggish, and consequently they have limited speed and accuracy. In most applications both accuracy and high speed of the manipulation are indispensable requirements of the system. Moreover, in some applications (e.g., aerospace applications) the weight of the manipulator becomes a critical consideration as well. It is clear that there is a marked contrast in satisfying all aforesaid requirements. Thus, the current solution for the problem is, in fact, a tradeoff between different requirements. Nonetheless, this is not a desirable solution in many applications. As a result, in the last few years, research has been conducted in the area of active vibration control. Successful vibration control facilitates fast, precise and accurate manipulation with large-scale but light weight manipulators. Along the same lines, piezoelectric materials have been studied as an excellent candidate for increasing the stiffness of a flexible structure by actively actuating the structure. Most of the work has focused on using a single piezoceramic bonded or laminated into a flexible structure. The flexible structures considered in these studies require a small amount of force. Unfortunately, in most practical applications, a single piezoceramic or even a set of piezoceramics cannot provide enough control authorities to overcome the unwanted vibrations in the system. In the current work, piezoelectric stack actuators have been studied as an alternative solution in which the actuator is not only capable of providing large control authorities but also it has the bandwidth and precision of a single piezoceramic. This allows for the suppression of vibrations in large-scale robotic systems during manipulation as well as when stationary.
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