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+++ title = "Comparison and classification of high-precision actuators based on stiffness influencing vibration isolation" author = ["Thomas Dehaeze"] draft = false +++
Backlinks
- [Actuators]({{< relref "actuators" >}})
- Tags
- [Vibration Isolation]({{< relref "vibration_isolation" >}}), [Actuators]({{< relref "actuators" >}})
- Reference
- (Ito and Schitter 2016)
- Author(s)
- Ito, S., & Schitter, G.
- Year
- 2016
Classification of high-precision actuators
| Categories | Pros | Cons |
|---|---|---|
| Zero stiffness | No vibration transmission | Large and Heavy |
| Low stiffness | High vibration isolation | Typically for low load |
| High Stiffness | High control bandwidth | High vibration transmission |
Time Delay of Piezoelectric Electronics
In this paper, the piezoelectric actuator/electronics adds a time delay which is much higher than the time delay added by the voice coil/electronics.
Definition of low-stiffness and high-stiffness actuator
- Low Stiffness actuator is defined as the ones where the transmissibility stays below 0dB at all frequency
- High Stiffness actuator is defined as the ones where the transmissibility goes above 0dB at some frequency
{{< figure src="/ox-hugo/ito16_low_high_stiffness_actuators.png" caption="Figure 1: Definition of low-stiffness and high-stiffness actuator" >}}
Low-Stiffness / High-Stiffness characteristics
- The low stiffness actuators achieve smooth transition from active isolation to passive isolation.
- The high stiffness actuators can have a gap between the passive and active isolation vibration where the vibrations are amplified in a certain frequency band.
Controller Design
{{< figure src="/ox-hugo/ito16_transmissibility.png" caption="Figure 2: Obtained transmissibility" >}}
Discussion
The stiffness requirement for low-stiffness actuators can be rephrased in the frequency domain as: "the cross-over frequency of the sensitivity function of the feedback system must be larger than \(\sqrt{2} \omega_r\) with \(\omega_r\) is the resonant frequency of the uncontrolled system".
In practice, this is difficult to achieve with piezoelectric actuators as their first resonant frequency \(\omega_r\) is too close to other resonant frequencies to ensure close-loop stability. In contrast, the frequency band between the first and the other resonances of Lorentz actuators can be broad by design making them more suitable to construct a low-stiffness actuators.
Bibliography
Ito, Shingo, and Georg Schitter. 2016. “Comparison and Classification of High-Precision Actuators Based on Stiffness Influencing Vibration Isolation.” IEEE/ASME Transactions on Mechatronics 21 (2):1169–78. https://doi.org/10.1109/tmech.2015.2478658.