The combination of extension and bending creates an elliptical motion of the tip, which can be used to impart motion to the stage. In this design, one or more ceramic fingers are preloaded against a ceramic spar, and piezo elements are used to drive the fingers in an oscillatory motion against the spar. Resonant piezo actuator offers extended travel (from millimeters to meters) with moderate resolution and is the most practical implementation of the piezo effect for travels beyond the range of stack actuators. In general, piezo stages with internal preload and closed loop position feedback can be useful positioners, but will provide limited travel, may be longer and more expensive than desired, and will be limited to moderate servo bandwidths unless the payload mass is quite small. The high Q of this resonance can complicate efforts to notch it out, and the end result is often that a lower than desired servo bandwidth must be accepted. The payload mass and the stiffness of the piezo stack produce a high Q resonance, the natural frequency of which can be surprisingly low for realistic tooling and part masses. When operated in closed loop mode, an additional concern arises. While the use of a linear position feedback transducer and a closed loop servo control can overcome hysteresis and drift, compared to the inherent simplicity of an open loop voltage commanded piezo stack, this comes at a considerable added cost and complexity. The motion in the piezo actuator continues to slowly creep after a position step. This can be as much as 15% of full travel. Significant amount of hysteresis or variation of travel versus applied voltage between forward and reverse movement.A stack capable of 200 microns of motion (the most common upper limit among commercially available devices) will typically be about 200 mm long. The number of plates grows with increased travel, increasing both stack length and cost as travel increases. Typical piezo stages range in travel from 10 to 200 microns. Housed piezo actuators with internal preload springs are useful, but suffer from several limitations, including: These limitations can be significantly reduced if the stack is mounted within a housing and if powerful springs are used to produce a high internal preload. Piezo linear actuators by themselves, are fragile and unable to produce force in both directions. ![]() The voltage applied to the piezo stack is distributed to each of the plates within the stack in a parallel configuration.ĭepending on the nature of the piezo material (soft versus hard), the applied voltage range is typically either +/- 1000 volts for hard or high voltage stacks, or +/- 120 volts for soft or low voltage stacks. ![]() The ratio L/L (change in length to length) for an applied voltage is quite small for a single piezoceramic element, and so most actuators are composed of a large number of thin plates, referred to as a piezo stack. Today, the most common materials used for piezo linear actuators are either barium titanate or PZT (lead zirconate titanate) ceramics. Superior lifetime of our actuators is guaranteed with the patented ceramic-encapsulated multilayer production process.The inverse piezoelectric effect was first discovered by Pierre and Jacques Curie in 1881. This group is specialized in research, design and manufacture of piezo materials and components for motion control. We currently employ 180 staff at our piezo ceramics division " PI Ceramic". PI offers the largest selection of standard and custom piezo actuators and engineered subassemblies. They provide efficient force generation because no conversion from rotary to linear motion and no gears or mechanical other parts that require maintenance or lubrication are involved. Piezoelectric actuators (also known as piezo transducers, or piezo translators) are based on the piezoelectric effect and convert electrical energy directly into linear motion with virtually unlimited resolution.
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