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Sensitivity Analysis and Optimal Control of a Nano-Newton CMOS-MEMS Capacitive Force Sensor for Biomedical Applications

Jalil Mozhdehi, Reza | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: English
  3. Document No: 43791 (58)
  4. University: Sharif University of Technology, International Campus, Kish Island
  5. Department: Science and Engineering
  6. Advisor(s): Meghdari, Ali; Selk Ghafari, Ali
  7. Abstract:
  8. In the first part of the thesis, we introduce the structure of a Nano-Newton CMOS-MEMS capacitive force sensor. This force sensor has been utilized out-of-plane sensing mechanism with high accuracy and reliability. Also, we discuss about sensitivity analysis of this force sensor. The largest change of capacitance (increased capacitance + decreased capacitance) occurs in ℓ=2/3. Sensitivity for increased capacitance grows by 8.33% and for decreased capacitance grows by 2.27%. The proposed method provides useful guidelines to increase the sensitivity of the sensor up to 250%. In the second part, a fixed structure controller, PID type, is proposed to control and suppress the in-plane vibration of the force sensor. Iterative Feedback Tuning approach is used to determine the optimal gains of the proposed controller for nonlinear dynamic characteristics of the system. The proposed optimal PID controller damped the vibration of the probe 30 times faster than the nonlinear controller proposed in literature. In the final part, we propose an optimal controller to prevent vertical vibration due to undesired out of plane excitations generated by environment or gripper during manipulation for the force sensor. To suppress the vibrational movement, a PZT 5A is used as actuation mechanism. To eliminate out of plane excitation, an optimal linear quadratic regulator is proposed using State-Space formulations. Simulation results illustrate that by employing optimum LQR control approach the maximum disturbance input is suppressed less than 0.7 sec with acceptable range of control voltage amplitude
  9. Keywords:
  10. Sensitivity ; Proportional-Integral-Derivative (PID)Controller ; Lead Zirconate Titanate (PZT) ; Linear Quadratic Requlator (LQR) ; Photo Sensor ; Electro Static Force ; CMOS-MEMS Sensor

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