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content/article/preumont02_force_feedb_versus_accel_feedb.md

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+title = "Force feedback versus acceleration feedback in active vibration isolation"
+author = ["Thomas Dehaeze"]
+draft = false
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+
+Tags
+: [Vibration Isolation]({{< relref "vibration_isolation" >}})
+
+Reference
+: <sup id="525e1e237b885f81fae3c25a3036ba6f"><a class="reference-link" href="#preumont02_force_feedb_versus_accel_feedb" title="Preumont, Fran\ccois, Bossens, \&amp; Abu-Hanieh, Force Feedback Versus Acceleration Feedback in Active  Vibration Isolation, {Journal of Sound and Vibration}, v(4), 605-613 (2002).">(Preumont {\it et al.}, 2002)</a></sup>
+
+Author(s)
+: Preumont, A., A. Francois, Bossens, F., & Abu-Hanieh, A.
+
+Year
+: 2002
+
+Summary:
+
+-   Compares the force feedback and acceleration feedback for active damping
+-   The use of a force sensor always give alternating poles and zeros in the open-loop transfer function between for force actuator and the force sensor which **guarantees the stability of the closed loop**
+-   Acceleration feedback produces alternating poles and zeros only when the flexible structure is stiff compared to the isolation system
+
+The force applied to a **rigid body** is proportional to its acceleration, thus sensing the total interface force gives a measured of the absolute acceleration of the solid body.
+Thus force feedback and acceleration feedback are equivalent for solid bodies.
+When there is a flexible payload, the two sensing options are not longer equivalent.
+
+-   For light payload (Figure [1](#org307b349)), the acceleration feedback gives larger damping on the higher mode.
+-   For heavy payload (Figure [2](#orgc0c4ad3)), the acceleration feedback do not give alternating poles and zeros and thus for high control gains, the system becomes unstable
+
+<a id="org307b349"></a>
+
+{{< figure src="/ox-hugo/preumont02_force_acc_fb_light.png" caption="Figure 1: Root locus for **light** flexible payload, (a) Force feedback, (b) acceleration feedback" >}}
+
+<a id="orgc0c4ad3"></a>
+
+{{< figure src="/ox-hugo/preumont02_force_acc_fb_heavy.png" caption="Figure 2: Root locus for **heavy** flexible payload, (a) Force feedback, (b) acceleration feedback" >}}
+
+Guaranteed stability of the force feedback:
+
+> If two arbitrary flexible, undamped structures are connected with a single-axis soft isolator with force feedback, the poles and zeros of the open-loop transfer function from the force actuator to the force sensor alternate on the imaginary axis.
+
+The same is true for the transfer function from the force actuator to the relative displacement of the actuator.
+
+> According to physical interpretation of the zeros, they represent the resonances of the subsystem  constrained by the sensor and the actuator.
+
+# Bibliography
+<a class="bibtex-entry" id="preumont02_force_feedb_versus_accel_feedb">Preumont, A., A. Fran\ccois, Bossens, F., & Abu-Hanieh, A., *Force feedback versus acceleration feedback in active vibration isolation*, Journal of Sound and Vibration, *257(4)*, 605–613 (2002).  http://dx.doi.org/10.1006/jsvi.2002.5047</a> [↩](#525e1e237b885f81fae3c25a3036ba6f)