The load applied to a piezoelectric actuator plays a crucial role in defining its performance. At a given voltage, the model described in Different actuator designs defines a characteristic line on the displacement vs. force diagram, where the actuator could be. The actual operating point (force, displacement) depends on the load.
For example, in the case of a simple positioning table where a piezoelectric actuator moves the table in the Z direction, the load is a simple mass. Upon initial loading, the element is compressed by the mass and the actuator moves (illustrated by the operating point moving from OP1 to OP2). After that, in quasi-static operation, the force applied on the piezo element by the load is a constant force, i.e. a vertical line on the displacement vs. force diagram (the operating point moving from OP2 to OP3). The actuator can therefore generate a displacement (curve B) sensibly equal to the free displacement (curve A).
In another ideal case, the load can be modeled by a spring. This spring has an elastic behavior, which can be represented on the displacement vs. force diagram by a straight line with a given slope. Upon actuation, the operating point of the system will follow this line (illustrated by the operating point moving moving from OP1 to OP2). The force applied on the actuator will increase as it expands. As a result, the actuator will generate a displacement (curve B) smaller than the free displacement (curve A) and a force lower than the blocking force.
In the general case, the load is a combination, an arbitrary curve on the displacement vs. force diagram. The load can even vary during operation, so it might be a set of curves. When designing a piezo-based system, it is important to ensure that all load cases are covered so the actuator can deliver the required performance in all conditions.
Our free 1.5 hour webinars follow the same structure as our tutorials.
We give you a competitive advantage by using our extensive knowledge to customize and optimize your piezo products. Thus, we will be your long-term piezo partner. Send your request today.
