Final Design Report

Platform Motion Measurement System

ELEC 492

A Senior Design Project, 2005 Between University of San Diego And Trex Enterprises

Submitted to: Dr. Lord at USD

Prepared by: YAZ Zlatko Filipovic Yoshitaka Yano

August 12, 2005 University of San Diego Final Design Report USD August 12, 2005 Platform Motion Measurement System

Table of Contents

I. Acknowledgments…………...…………………………………………………………4

II. Executive Summary……..…………………………………………………………….5

III. Introduction and Background…...………………………...………………………….6

IV. Project Requirements……………...... 8

V. Methodology of Design Plan……….…..……………..…….………….…..…….…..11

VI. Testing….……………………………………..…..…………………….……...... 21

VII. Deliverables and Project Results………...…………...…………..…….…………...24

VIII. Budget………………………………………...……..……………………………..25

IX. Personnel…………………..………………………………………....….………...... 28

X. Design Schedule………….…...……………………………….……...…………...... 29

XI. Reference and Bibliography…………..…………..…………………...…………….31

XII. Summary…………………………………………………………………………....32

Appendices Appendix 1. Simulink Simulations…..………………………….…….33 Appendix 2. VisSim Simulations...... ……………………………….34 Appendix 3. Frequency Response and VisSim results……………...... 36 Appendix 4. Vibration Measurements…………..………………….….38 Appendix 5. PCB Layout and Schematic……………………………..39 Appendix 6. User’s Manual…………………………………………..41

Appendix 7. PSpice Simulations of Hfilter…………………………….46

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List of Figures and Tables

Figure 1. A Moving Platform………………………………………………………….…..6

Figure 2. Micro-Electro-Mechanical-System (MEMS) sensor..…..…….……………….7

Figure 3. Magneto-Hydro-Dynamic (MHD) gyro.………………...………………….…7

Figure 4. Range of frequencies covered by the final product……………………………7

Figure 5. The working principles behind MHD sensor……………………..…………...8

Figure 6. The working principles behind MEMES sensor………………………………8

Figure 7. Vibration Generator System block diagram…………………….……………11

Figure 8. Transfer function of MHD and MEMS...……………………………….……12

Figure 9. Synthesis Method (MathCad)…………..……………………………….……13

Figure 9a. Blended frequency response, MHD filter response, and MEMS frequency response (MathCad)………………………….…...………13

Figure 10. Blending system…………………………….....……………………………14

Figure 11. Low-pass section realization for the first order filter…………………….…15

Figure 12. Hfilter for the X-axis …………….…..……..…………...……………………16

Figure 13. Gfilter and the blending circuitry …………..……..…………...…………..…17

Figure 14. 5V and -2.5V references and zero MEMS offset …………..……..…………17

Figure 15. Experimental vibration measurements…………………………………….....19

Figure 16. Complete system simulation at 10 Hz……………………………………...... 20

Table 1. Low and high frequency vibration measurements……………………………18

Table 2. Test Plan……………………………………………………………………...21

Table 3. Sponsor Requirements and Accomplishments……………………………….24

Table 4. Budget…………………………………………….…………………………..25

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Table 5. Member’s task list …..………………………………………………………..28

Table 6. Gantt chart……...…………...………………...………………………………..29

List of Figures for Appendices

Appendix1 Fig1. Vibration Generator System-Simulink...…………………………….33 Appendix1 Fig2. Output of Control system…………………………………………….33 Appendix1 Fig3. Code to generate the plot ……………………………………………33

Appendix2 Fig1. Vibration Generator System-VisSim……..………………………….34 Appendix2 Fig2. MEMS output………………………………………………………..34 Appendix2 Fig3. Step input………………………….…………………………………35

Appendix3 Fig1. Y-axis: Simulated blended frequency response …………...……..…....36 Appendix3 Fig2. Z-axis: Simulated blended frequency response.…….………...…..…...36 Appendix3 Fig3. Block diagram for the blended system.…….………...…………….…...37

Appendix4 Fig1. Z-axis vibration measurements…………………………….………….38 Appendix4 Fig2. Y-axis vibration measurements …………………………………...….38

Appendix5 Fig1. PCB Layout of the complete system……………………….………….39 Appendix5 Fig2. XYZ Hfilters…………………………………………………………….39 Appendix5 Fig3. Gfilers and the blending circuitry……………………………………….40 Appendix5 Fig4. MEMS offset and the voltage reference……………………...……….40

Appendix6 Fig1. PCB layout…………………………………………………………….42 Appendix6 Fig2. -2.5V offset with jumpers.…………………………………………….44 Appendix6 Fig3. MEMS directional rotation...………………………………………….45

Appendix7 Fig1. X-axis Frequency response in PSpice……...………………………….46 Appendix7 Fig2. H X-axis filter design……....………………………………………….46

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I Acknowledgments

We would like to thank the people who helped make this project possible. For encouragement, for understanding, and for the use of their equipment and time, our heartfelt thanks go to Trex Enterprises. Mr. Mike Borrello, of Trex Enterprises, made many suggestions on our design which improved the outcome of many tests preformed on the system. With his constant help, the project deadlines were accomplished. The University of San Diego provided the use of lab and the funds for the equipment. We would also like to thank Dr. Kanneman and Dr. Lumori for their help in the design of the vibration generator system, without them the final control system would not have been as accurate as it is. Dr. Pateros introduced us to this project and to the wonderful people at Trex Enterprises and helped us with the PCB (Printed Circuit Board) layout, and we thank him for that. We would like to express particular appreciation to Dr. Susan Lord for reviewing the documents. She made many suggestions and contributed special insights and details to the CDR (Critical Design Review), the FPDR (Final Project Design Report) and the final project binder.

We would also like to express our gratitude to the people at Visual Solutions who provided us with the free VisSim software which was used as a primary real-time simulation tool.

Sponsor

This project was made possible by Trex Enterprises. Trex Enterprises is the leader in optical design and test equipment that support adaptive optics, tracking and laser programs. The design capabilities include Computer Aided Design systems for multi- purpose analyses. “There are extensive facilities to support laser research employing various IR and visible solid-state lasers. Our electronic facilities support research on signal processing, millimeter wave systems, custom digital interfaces and high voltage analog electronics for a variety of applications. Trex Enterprises' engineering facilities include materials research and engineering test labs, electronics design space, as well as mechanical design, electro-optic and electro-acoustic labs” (www.trexenterprises.com).

Special thank you to: Ms. Anne Pol, CEO of Trex Enterprises Mr. Eric Woodbridge, Laser Communication Manager Mr. Mike Borello, Senior System Engineer at Trex Enterprises Mr.Peter Darnell, President of Visual Solutions Mr.Rich DiManno, Visual Solutions

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II Executive Summary

The vibrations experienced by the disturbances on any moving platform cause mounted systems to be unstable and unreliable. The vibrations can vary from very low to very high frequencies. It is important to measure the amplitude and frequency of vibrations and to use these data to design more efficient and accurate mounted systems. Using high frequency sensors, such as Magneto-Hydro-Dynamic (MHD) sensors, integrated with low frequency sensors, such as Micro-Electro-Mechanical-System (MEMS) sensors, a large range of vibrations can be measured.

The goal of this two semester senior design project at USD was to design and implement a filter that allow these two sensors, MEMS and MHD, to act as one single sensor that can detect both low and high frequency vibrations from about 0.01 Hz to 1000 Hz. Combining these two sensors produces an efficient and accurate measuring tool that allows users to model vibrations over a large range of conditions. To measure the accuracy of the tool, it was necessary to add an additional design task and deliverable. Specifically the design of the vibration generator system (VGS) that generates low frequency vibrations (up to 20 Hz) that was used as a testing tool for the sensors.

Using the MEMS’s and MHD’s transfer functions (TF) and the synthesis method (TFMHDxGfilter + TFMEMSxHfilter = TFBLEND) the blended output was obtained. The synthesis method produced a 11th order Hfilter and a unity gain Gfilter. The Hfilter was simplified to a 3rd order filter by canceling the poles that were too close and poles that rd were out of the frequency range. The 3 order Hfilter and a unity gain Gfilter were implemented and built. Implementing these two filters, along with the blending circuitry for MEMS and MHD, on a PCB board a new sensor capable of measuring both low and high frequency vibrations, from about 0.01 Hz to 1000 Hz, was created. Although the sensor was designed to measure frequencies up to 1000 Hz, the actual measurements were only preformed up to 20 Hz due to the vibration generator’s mechanical limits. The new blended sensor preformed with average 90% accuracy.

The final product was delivered to Trex Enterprises on August 12, 2005. The deliverables were a simulation and a PCB board. The simulation was hardware in the loop simulation demonstrating blending of the MEMS and MHD sensors and the wide range for vibration detection. The demonstration was executed on a single axis gimbal and the potentiometer rate was used as a true measurement for comparisons. The vibration generator system generated low and high frequency vibrations (0.01-20 Hz) that were measured using the final product.

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III Introduction and Background

Today’s world of the high-tech demands speed, efficiency and accuracy of systems used in everyday life. Airplanes, cars, boats, and jetfighters are equipped with very sensitive systems that might fail if certain conditions are not met. Moving platforms (Figure 1) such as cars and airplanes experience vibrations from very low to very high frequencies. The vibrations at low frequencies are due to slow sway experienced by the moving platforms, and the high frequency vibrations are due to disturbances such as (road friction, bad weather and etc). It is important to minimize these factors for mounted systems to perform efficiently. The mounted systems located on these platforms can be very unstable due to vibrations and might for example generate useless data. To prevent such problems, mounted systems need to be designed to compensate for vibrations over a large frequency range. Using a vibration sensor the vibrations can be modeled and new mounted systems can be efficiently designed using these models.

Figure 1 A moving platform

To design more efficient systems on moving platforms, Trex has tested angular rate sensors which use MHD (Figure 3) technology to accurately measure vibrations. However, these sensors fail to detect vibrations at very low frequencies. Since airplanes and boats can sway slowly, it is necessary to cover frequencies as low as 0.01 Hz or less. To measure low frequencies, another sensor is required. A good candidate for a low frequency sensor is a MEMS (Figure 2) gyro since it can measure frequencies down to 0.01 Hz. Combining these two sensors produced a very efficient and accurate measuring tool that will allow users to design accurate mounted systems that would be able to perform under a wide range of frequency vibrations (Figure 4).

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Figure 2 Micro-Electro-Mechanical- Figure 3 Magneto-Hydro-Dynamic (MHD) System (MEMS) gyro gyro

Blended Output

MHD

MEMS

0.01 10 1000 Frequency (Hz)

Figure 4 Range of frequencies covered by the final product Background MEMS and MHD are excellent sensors for angular motion measurement and control. Magnetohydrodynamic (MHD) sensors acquire the measurement of angular rate. According to Applied Technology Associates (ATA, a leading manufacturer of MHDs), “the technology has demonstrated its feasibility in areas of automotive safety research instrumentation; line of-sight (LOS) stabilization for handheld and platform mounted imaging systems and sensor controlled LOS stabilization; and defense related space based pointing and tracking experiments” (http://www.atasensors.com/). The MHD has been proven to work at very high frequencies (1,000 Hz), but fails to perform at very low frequencies (<1 Hz). This is where the MEMS sensors are of most importance. These small inexpensive sensors have been tested at very low frequencies, and the results were phenomenal. These Micro Electro Mechanical Systems operate at almost 0 Hz.

The way that MHDs work is illustrated in Figure 5, “an angular motion about the sensitive axis of the sensor results in a relative velocity difference between the fluid proof mass, which is highly conductive, and the normally applied static magnetic field, which moves with the sensor case. This relative velocity difference between the

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conductive fluid and the magnetic field generates an electric potential across the channel that is sensed directly by several versions of the MHD device” (http://www.atasensors.com/).

Figure 5 The working principles behind MHD Figure 6 The working principles sensor behind MEMES sensor

The working mechanism behind the MEMS sensor is illustrated in Figure 6. Polysilicon springs are suspended in such a way that the body of the sensor (known as the proof mass) can move in both the X and the Y axes. “Acceleration causes motion of the proof mass. Around the four sides of the square proof mass are 32 sets of radial fingers (only 2 of radial fingers are shown in the Figure 6). These fingers are positioned between plates that are fixed to the substrate. Each finger and pair of fixed plates make up a differential capacitor, and the deflection of the proof mass is determined by measuring the differential capacitance. This sensing method has the ability of sensing both dynamic acceleration (i.e. shock or vibration) and static acceleration (i.e. inclination or gravity)” (www.memsnet.org).

IV Project Requirements

All of these requirements were specified by Trex Enterprises.

General Requirements As a senior student project, the team shall be expected to deliver and demonstrate a modified Platform Motion Measurement System design providing accurate rate motion measurement from 0.01 to 1000 Hz by designing and fabricating circuitry to operate actual MEMS gyros and blend measurements from these sensors with simulated MHD rate sensor signals derived from test platform angle measurements.

Specifications Sensor Head Packaging Not required

Sensor Head Connector the circuit board containing the blending filters shall provide connector interfaces TBD (to be determined) by the student team allowing the sponsor (at

8 Final Design Report USD August 12, 2005 Platform Motion Measurement System a later date) to fabricate interface cables for system integration with the MHD and data recording system.

Blending Filters The blending filters shall provide interface between the MEMS gyros and simulated MHD sensors and the blended output signal. Three independent, but not necessarily the same blending filters are required for roll, pitch and yaw.

Blended Voltage Output The blended output shall replace the existing MHD sensor output which requires a ± 10 volt signal. This maximum signal range shall be scaled to the existing angular rate of the MHD sensors.

Frequency Response The system shall provide a band limited frequency response with a lower – 3 dB cutoff at 0.01 and upper -3dB roll-off at 1000 Hz.

Accuracy the accuracy of the blended rate, determined by the measured output signal between frequencies ranging from 1 and 100 Hz shall be < 1% of true input rate.

Number of channels There shall be 3 independent channels (roll, pitch and yaw) of blended output.

Power Consumption The power consumption of the integrated MEMS sensors and blending circuit shall not exceed 3.0 W

Deliverables 1) Document(s) and or files describing blending filter design in terms of a. Synthetic derivation of the design b. Transfer functions for 3 channels c. Analysis, simulation validating design 2) Document(s) and or files describing the electronics design including a. The blending filter b. PC board design c. Interface connection diagram 3) Assembled blended filter PC board 4) Documented test results that verify operation of the blending filter

Goal The first goal of this project was to design and build a vibration generator system that measures very low frequencies using Micro-Electro-Mechanical-System (MEMS) sensors. The second goal was to use these low frequency measurements along with high frequency measurements, generated by Magneto-Hydro-Dynamic (MHD) sensors, to design and implement a filter that allowed these sensors (MHD and MEMS) to act as one single sensor. The project was completed at the end of the summer of 2005.

Market The project was sponsored by Trex Enterprises and the final product was built for their use. The market for vibration detection sensors includes military and civilian users. This

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measuring tool promises great improvements in the way that new systems are designed and mounted onto moving platforms. Such improvements would be especially valuable in applications such as communication between jetfighters where these sensors would allow jetfighters to transmit and receive accurate data without major errors perhaps even saving lives. Although this tool would be beneficial, the cost would not be low, for Magneto- Hydro-Dynamic (MHD) sensors are very expensive ($20,000). This might not look cost efficient, but if the average price of a jetfighter, a tanker, or a tank is considered, this cost is negligible. Therefore Trex’s customers, such as the military, are perhaps most likely to benefit from this tool.

These MHD and MEMS sensors have been used individually in many applications, but never as one integrated sensor. It was the task of this project to integrate these two sensors to work as one over a wide range of frequencies (0.01 Hz-1000 Hz).

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V Methodology of Design Plan

Vibration Generator System To measure the accuracy of the blended filter, it was necessary to add an additional design task and deliverable. Specifically the design of the vibration generator system (VGS) that generates low frequency vibrations (up to 20 Hz) that was used as a testing tool for the sensors. The new task was discussed and agreed upon with the sponsor.

The VGS was designed using control system methods. VGS is a position control system that uses a PD (proportional derivative) controller and an amplifier as a control device. The linear voice coil actuator is used to move the platform-gimbal. The reason we used a PD controller can be attributed to its good performance in a wide range of operating conditions and partly to its functional simplicity. To get the system to respond in less than 20 msec it was necessary to implement such a controller. The PD controller was calibrated to give the fastest transition without an overshoot (critical damping) to minimize the time constant. Using the ITAE (integral of the time multiplied by absolute error) and the closed loop transfer function the Kp (proportional gain) and Kd (derivatve gain) constants were determined producing a 3 msec time constant. Although 3 msec time constant was obtained, due to the gimbals mechanical issues we had to adjust the time constant to 20 msec. This 20 msec time constant translates into 0.05-20Hz frequency range which detriments the range of the experimental verification for the sensor.

Figure 7 shows the VGS. The VisSim real-time blocks (within the PC) were used to simulate the signal generator, the summing junction and the PD controller. The generated signal from the PD controller goes through a DAC (digital to analog converter) and is fed into the linear voice coil actuator (the motor) which mechanically vibrates a single axis gimbal. These vibrations simulate the vibrations experienced by a moving platform. The MEMS sensor is mechanically attached to the gimbal. The output voltage from the MEMS, which is directly proportional to the angular rate (rad/sec) of the vibrations, is measured.

Figure 7 Vibration Generator System (VGS) block diagram

The single axis of the gimbal is attached to a potentiometer and the output voltage is directly proportional to the angular displacement (radian). The voltage output is fed back

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into the summing junction and differentiated within VisSim to obtain a true measurement which represents angular rates (rad/sec), just like an output from a real MHD.

More details on this system can be found in Appendix 1 and 2. This system was designed and tested with a real MEMS sensor and a virtual MHD sensor. The data obtained from the tests preformed can be viewed in Appendix 4.

Sensors Transfer Functions The transfer functions of both sensors were necessary for this project. Using the MHD’s data and the frequency response provided by ATA we were able to obtain the MHD transfer function (eq.1) which was used to build a virtual MHD sensor in VisSim. The MHD sensor had to be virtually built within VisSim due to the lack of availability and the high cost of the real MHD. The virtual MHD sensor preformed as expected. It detected high frequency vibrations (above 1 Hz), but it failed to detect low frequency vibrations (below 1 Hz).

The MEMS transfer function (eq.2) was obtained using the data from the datasheet (from Analog Devices) and the tests proved the validity of the given data. Figure 8 shows the frequency response of both TF.

39 jjjjje ωωωωω ++++ )5.565)(7.28)(3.60)(4.21(833.2 TMHD = eq )1.( jjjjjjjj ωωωωωωωω ++++++++ jω+ )2.18221)(3.16336)(3.584)(3.251)(1.69)(6.17)(1.5)(5.3)(8.1(

π 24004 T =10 eq )2.( MEMS + + jj ωπωπ )4002)(102(

Figure 8 Transfer Function of MHD (red) and MEMS (blue)

Synthesis Method Using the MEMS’s and MHD’s transfer functions (TF) and the synthesis method (TFMHDGfilter + TFMEMSHfilter = TFBLEND, Figure 9) the blended output (Figure 9a) was obtained. Passing the sensors’ outputs through filters and adding the filters’ outputs, the

12 Final Design Report USD August 12, 2005 Platform Motion Measurement System ideal blend (flat frequency response) was obtained. The MEMS’s TF was multiplied by an unknown H-filter, added to the MHD’s TF, which was multiplied by a G-filter (unity gain), and equated to an ideal filter. After solving for an unknown H-filter, the ideal blend of frequencies (from 0.01 Hz to 1000 Hz) was achieved.

Figure 9 Synthesis Method (MathCad)

Figure 9a Upper Left: Simulated blended frequency response (pink), MHD frequency response (red) and MEMS frequency response (blue) Lower Right: Hfilter’s frequency response (black) and Simulated blended frequency response (pink)

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Blending system Using the real MEMS and virtual MHD along with the virtual H-filter, the complete system was simulated. The results were as expected. The measuring tool performed well at both high and low frequencies. The output of the blended filter followed the output of the true measurement (which is the true angular measurement of gimbal’s motion, Table 1). Figure 16 shows the blended output following the true measurement at 10 Hz. Due to VGS constraints, the test could only be performed up to 20 Hz.

Figure 10 shows the blending system within VisSim. The signal from the pot derivative (the true measurement) is fed into the virtual MHD. The synthesis method (described in Synthesis Method section) produced a 11th order Hfilter and a unity gain Gfilter. Initially, we had a 11th order design and we put in a lot of effort to minimize the design. Expressing the 11th order transfer function as partial fractions, eight 1st order and two 2nd order TF were obtained. Among these poles, five 1st order and two 2nd orders had poles that were close in frequency and amplitudes that canceled each other. Then, we plotted the simplified transfer function with MathCad and found that implementation of the transfer function is easier with three 1st order filters rather than with one 3rd order filter. Although the 1% accuracy required by Trex Enterprises was relaxed, the 3rd order provided a more efficient design. 11th order filter would require a lot of time to implement, build and it would have been cost ineffective. On the other hand the 3rd filter was easy to implement and it reduced the board space. The signals from the MHD and MEMS go through G and H filters to make the total frequency response flat. Finally, the outputs of the G and H filters are virtually added to produce the blended output with a wide range of frequencies (0.01Hz – 20Hz).

Figure 10 Blending System

Hardware Implementation Hfilter Design rd Using the 3 order Hfilter transfer function (frequency response of the Hfilter can be seen Figure 9) and the first order low pass filters we obtained an efficient design. To implement the Hfilter we decided to use an analog design instead of a digital design. Although a digital design would have many benefits, such as less time to implement and easy design change, the benefits were out-weighed by the cost and the PCB board size. To implement a digital filter Matlab, or other software, would be required along with the board that supports these software. This could get very expensive. Although a digital filter could be built on the board using OpAmps and sampling circuitry, the adjustments to the design would not be as easy to make as with the Matlab software and the Matlab’s data acquisition board, which would be the reason for going digital. Figure 11 shows the low pass section realization for the first order filter. The design required three first order low pass filters, two inverters and a summer (using LM 348). Instead of making one 3rd

14 Final Design Report USD August 12, 2005 Platform Motion Measurement System order filter (combination of 1st and 2nd order filters), we decided to make three 1st order filters.

The response of the first order OpAmp filter stage was described by the transfer characteristic: v + /'1 RR o = vi 1+ ω CRj 11

The resonant frequency ωo of the circuit was determined by the transfer function of the Hfilter .Therefore the input RC time constant was found by the following equation:

1 1 ωo CR 11 =>−= CR 11 ωo

Finally, the low-frequency gain which was obtained from the TF in Figure 8 allowed us to find the R’ and R values of the circuit using the following equation:

AV o /'/'1 ARRRR V o −=>−+= 1

Figure 11 Low-pass section realization for the first order filter

(Note: the above theory and the methodology was obtained from Active and Non-linear electronics by Schubert and Kim)

We designed our system using Butterworth filters instead of Chebyshev or Elliptical filters. We wanted to measure the vibrations accurately, so we used Butterworth which has the flattest frequency response. Although Chebyshev and Elliptical filters have smaller transition region comparing with Butterworth, Chebyshev and Elliptical filters have non-linear ripples. Therefore, due to the non-linear riples it is hard to tune a filter to the specific poles (frequencies).

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Using the Hfilter transfer function from Figure 9 and the method stated above the design for the X, Y and Z-axis in Figure 12 (only design for X-axis shown, other designs (Y and Z) have slightly different resistor values) was obtained. The inverter was used to change the polarity to the original input polarity.

Blending System Design As shown in Figure 13, the blending circuitry for G and H filters was obtained using inverting and non-inverting (to make the output positive) amplifiers. The signals from the MHD and MEMS go through G and H filters to make the total frequency response flat. Finally, the outputs of the G and H filters are added to produce the blended output with a wide range of frequencies. Since the Gfilter is a unity gain filter we built a non- inverting amplifier to allow the users to adjust the MHD gain if necessary. Since the gain of the real MHD sensor can vary it might be necessary to adjust the gain by adding appropriate resistors. The Gfilter is a non-inverting amplifier and its gain (Av = 1+MHa2/MHa3) can be adjusted by choosing the right values for MHa2 and MHa1 resistors. The current PCB design allows for the Gfilter, but it is not used.

Figure 12 Hfilter for the X-axis

Because the MEMS has 2.5 V offset, we had to build a - 2.5 V voltage reference. (To learn more about the 2.5 V reference see the user’s manual). Using a LM337 (voltage reference) and a summer (LM348) we obtained a 0 V offset for MEMS (Figure 14). The MEMS sensor requires a 15 V DC power (this is comes from the power supply) and a 5 V DC input. Therefore we had to build a 5 V voltage reference (Figure 14).

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Figure 13 Gfilter and the Blending circuitry

Figure 14 5V and -2.5V references and zero MEMS offset

To see the complete PCB layout of the whole system please see Appendix 5.

PCB Design We began our design by drawing a schematic with ExpressSCH program. The schematic was then linked to the PCB file to indicate necessary connections, for example it highlighted the pins that should be wired together in blue.

Using LM348 OpAmps we were able to save space on the board, because LM348 has four 741 operational amplifier per chip. We place the connectors at the edge of the board for easy access. The 2kΩ potentiometers were placed on the edge of the board for easy adjustments. We designed a 4 layer board using the ExpressPCB. Dr. Pateros, project advisor, suggested that we should use the 1st layer as the +15V DC power input and the 2nd layer as the -15V DC input. This prevented voltage from being exposed. He also

17 Final Design Report USD August 12, 2005 Platform Motion Measurement System suggested that the ground should be placed as a layer to avoid ground loops. With Dr. Pateros input and many checks by both team members the board needed only one revision.

The board size is 4.5” x 7.8”.

The PCB contains the following: o Sensor Head Connector Blending filters have a connector interface allowing Trex to interface the system with the MHD o 3 Blending Filters (each for 3 channels) Blending filters provide interface between MEMS and MHD o H and G filters o -2.5 V DC and 5 V DC reference o Power connectors o Input/output connectors For more information on the PCB see Appendix 4 and the user’s manual.

Integration and Testing The board was populated on August 3, 2005 and the final tests were conducted on August 4, 2005. Table 1 shows the final results. The results prove that the product performs as expected. The blended output follows the true measurement (PotRate) over a wide range of frequencies (from 0.01 Hz-20 Hz). Although the average % error was less than 11%, it did not meet the 1% requirement on the 1Hz-20Hz frequency range in the sponsor’s requirement. This is due to the design simplifications and the accuracy of MEMS and MHD sensors itself. The original design was too complex and more expensive to build; it required a 11th order filter. Although simplifying the original design to the 3rd order filter was not easy, the new design proved to be cheaper and effective. To obtain the new design the 1% error was relaxed to <12%. Due to noise, the MEMS’s and MHD’s accuracy the 1% error was impossible to achieve.

Table 1 Low and high frequency vibration measurements (See Appendix 4 for the complete table and Figure 15 for the plot) (note: PotRate is the potentiometer derivative and is used for true measurement and blend out is combination of MHD and MEMS through H and G filters)

Input frequency Blend MHD PotRate (Hz) Input(degree) out(deg/s) MEMS(deg/s) (deg/s) (deg/s) Error (%) 0.05 3 0.015000 0.015000 0.000000 0.015000 0 0.06 3 0.020000 0.020000 0.000000 0.020000 0 0.07 3 0.025000 0.025000 0.000000 0.025000 0 0.08 3 0.028000 0.028000 0.000000 0.028000 0 0.09 3 0.030000 0.030000 0.000000 0.030000 0 0.1 3 0.034000 0.034000 0.000000 0.034000 0 0.2 3 0.070000 0.070000 0.010000 0.070000 0 0.3 3 0.100000 0.100000 0.025000 0.100000 0 0.4 3 0.200000 0.200000 0.050000 0.200000 0

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0.5 3 0.250000 0.250000 0.075000 0.250000 0 0.6 3 0.300000 0.300000 0.100000 0.300000 0 0.7 3 0.350000 0.350000 0.150000 0.350000 0 0.8 3 0.400000 0.400000 0.200000 0.400000 0 0.9 3 0.460000 0.460000 0.220000 0.460000 0 1 3 0.450000 0.450000 0.300000 0.450000 0 2 3 0.800000 0.600000 0.700000 0.750000 6.666667 3 3 1.100000 0.700000 1.000000 1.000000 10 4 3 1.800000 0.600000 1.500000 1.500000 20 5 3 2.040000 0.630000 1.800000 1.800000 13.33333 6 3 2.280000 0.630000 2.040000 2.100000 8.571429 7 3 2.400000 0.630000 2.100000 2.250000 6.666667 8 3 2.700000 0.630000 2.550000 2.700000 0 9 3 3.000000 0.750000 2.700000 2.700000 11.11111 10 3 3.600000 0.750000 3.000000 3.300000 9.090909 11 3 3.600000 0.750000 3.300000 3.300000 9.090909 12 3 4.500000 0.750000 4.140000 4.200000 7.142857 13 3 5.100000 0.720000 4.800000 4.800000 6.25 14 3 4.800000 0.750000 4.800000 4.800000 0 15 3 5.520000 0.750000 5.100000 5.100000 8.235294 18 3 5.400000 0.600000 4.800000 4.800000 12.5

In other experimental tests preformed using the vibration generator system, MEMS performed well at low frequencies (as low as 0.01 Hz) and failed to perform at higher frequencies. Table 1 shows that at low frequency vibrations (below 1Hz) MEMS follows the blended output, but MHD does not. On the other hand, at higher frequencies MHD performs well, but MEMS fails.

Vibration Measuerements

7

6 y = 0.3194x

5

4

3 Rate (rad/sec) 2

1

0 024681012141618 Frequency(Hz)

Blend Mem s MHD PotRate Linear (MHD) Figure 15 Experimental vibration measurements Figure 16 shows an example of a simulation that has been done in VisSim. The blended output (pink) follows the true measurement (potrate-brown) at 10Hz. The graph also

19 Final Design Report USD August 12, 2005 Platform Motion Measurement System illustrates that the MEMS (blue) sensor has saturated at this frequency. On the other hand, the MHD (red) sensor follows the true measurement at this frequency. The plot of experimental data in Figure 15 also shows the MEMS saturated and the MHD following the true measurement at 10 Hz.

Figure 16 Complete system simulation at 10 Hz Blue-MEMS output (rad/sec) Red-MHD output (rad/sec) Pink-Blended output (rad/sec) Brown-PotRate (rad/sec)

User’s manual Detailed instructions to how to connect the PCB board can be found in Appendix 6. These instructions have been tested by both members of this team. The manual was also tested by Lovelyn Mangat, a senior electrical engineer student at USD.

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VI Testing

The final product was tested on August 3, 2005. Many simulations were conducted before August. First we have designed and simulated the blended filter using MathCad and PSpice. These tests were conducted early in the first semester to give us an idea of what the final deign should look like. The vibration generator was also designed and simulated. This was done on February 20, 2005. All of the vibration generator system stages were built in May 2005 and initial tests were conducted. The second semester was dedicated to building and testing the integrated filter. The physical tests were mostly conducted during the summer semester; the spring semester was dedicated to simulations.

Table 2 shows what has been tested and simulated and what software was used for simulation.

Table 2 Test Plan Item Task Date of Completion

1 Simulate MHD transfer function (Simulink) February 2005 2 Simulate MEMS transfer function (Simulink) February 2005 3 Simulate Vibration Generator system (Simulink) March 2005 4 Simulated integrated MHD + MEMS filter (MathCad) March 2005 5 Simulate Vibration Generator System (VisSim) April 2005 6 Real time tests of the complete physical system May 2005 (VisSim) 7 Real time tests of the physical control system with the June 2005 fixed gimbal (VisSim) 8 Simulate MHD transfer function with the new data June 2005 (MathCad, Maple) 9 Simulated integrated MHD + MEMS filter (MathCad) June 2005 10 Simulate virtual MHD (VisSim) June 2005 11 Simulate virtual H-filter (VisSim) June 2005 12 Real time tests of the physical control system with June 2005 virtual components (VisSim) 13 Simulate blended outputs and H-filter June 2005 14 Simulate PSpice July 2005 15 Test real H-filter July 2005 16 Test PCB board August 2005 17 Test complete system with the PCB board August 2005 18 Test three axis filter August 2005

Items 1,2, and 3 - Transfer function blocks for MHD and MEMS were simulated in Simulink - Checked if MHD is attenuated at high frequencies above 10 Hz - Checked if MEMS output is attenuated at lower frequency (<10Hz)

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- VGS designed using MEMS’s and MHD’s TF - The time constant of the VGS was determined to be 20 ms

Items 5, 6, and 7 - VGS was simulated with VisSim - The time constant of the VGS was determined to be 20 ms - VGS control loop was built using hardware such as current amplifier, motor, gimbal, potentiometer, data acquisition board, and computer - The connector between the gimbal shaft and motor was loose, so we brought it to Trex Enterprises to be repaired - VGS tested with the fixed gimbal, time constant of 20 ms

Item 8 and 9 - More accurate data was received MHD from ATA and the MHD’s TF was updated - The Bode plot of the MHD TF had not changed - We solved the synthesis equation and determined the transfer function of Hfilter. We plotted the transfer functions of MHD, MEMS, Hfilter, and output of the integrated filter. The output of the integrated filter showed flat frequency response from 0.01 Hz to 1000 Hz.

Item 10 and 11 - We build the control blocks for MHD and Hfilter with VisSim. We verified that the simulated output matches with the Bode plot made within MathCad.

Item 12 and 13 - The complete system was tested (VGS, real MEMS, virtual MHD, and virtual Hfilter) - The blended output followed the pot derivative (derivative of angular displacement) from 0.05 to 20 Hz.

Item 14 and 15 - Resistors’ and capacitors’ values were determined from the transfer function of Hfilter - The circuit was designed and tested with PSpice (Appendix 7). The Bode plot of the circuit matched with the Bode plot of H filter’s transfer function. - We implemented the H filter on a bread board and tested our system with real MEMS, virtual MHD, and real H filter.

Item 16, 17, and 18 - We designed a PCB board and traced all of the wiring to make sure that all wiring was right. We ordered the board from expresspcb.com. - When the board arrived we tested that +/-15 V DC power supply and ground to make sure that they were not shorted - Each stage was tested as we populate the board

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- We tested our system with real MEMS, virtual MHD, and real Hfilter on the PCB board. - We observed that blended output of all X, Y, and Z axis followed the pot derivative (true measurement) from 0.05 to 20 Hz with the populated PCB board.

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VII Deliverables of Project Results

The final product was delivered to Trex Enterprises on August 12, 2005. The deliverables were a simulation and a piece of hardware. The simulation was hardware in the loop simulation demonstrating blending of the MEMS and MHD sensors and the wide frequency range for vibration detection. The demonstration was executed on the single axis gimbal and the potentiometer rate was used as a true measurement for comparisons. The vibration generator system generated low and high frequency vibrations (0.01-20 Hz) that were measured using the final product. Experimental data (such as Figure 11) along with frequency response was provided to prove that the product can cover these frequencies. The final product consists of three filters on a PCB board and three channels of independent circuitry for blending the outputs. The three filters correspond to the three orthogonal axes required by MHD sensors. Although the blended outputs cover a wide range of frequencies from 0.01 Hz-1000 Hz, the experiments were preformed up to 20 Hz due to VGS’ mechanical constrains.

Final deliverables: o The final product that consist of three filters on a PCB board and three channels of independent circuitry for blending the outputs. The three filters correspond to the three orthogonal axes required by MHD sensors. o The blended outputs will cover a wide range of frequencies from 0.01 Hz- 1000 Hz. o Final project report for the second semester o The simulation will be hardware in the loop simulation demonstrating blending of the MEMS and MHD sensors and the extension of the lower frequency range for vibration detection. The demonstration will be executed on the single axis gimbal. The vibration generator system will generate low and high frequency vibrations (0.01-20 Hz) that will be measured using the final product.

Objectives accomplished Table 3 Sponsor requirements and accomplishments Requirements Trex Requirements Project Results Accomplished

Sensor Head Required Blending filters have a YES Connector connector interface allowing Trex to interface the system with the MHD Blending Filter Required Blending filters provide YES interface between MEMS and MHD Blended Voltage Required The output replaces the YES Output existing MHD sensor output Frequency Response 0.01-1000 Hz The design provides the YES frequency response from 0.01-1000 Hz. The tests were conducted up to 20Hz due to mechanical limitations of VGS.

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Accuracy <1% from 1-100Hz <10% from 0.05-20 Hz Relaxed by the sponsor Number of Channels 3 There are 3 independent YES channels for roll, pitch and yaw. Power Consumption <3W ~1.5W YES

VIII Budget

The financed support for this project was provided by Trex Enterprises and Associated Students Budget (ASB). All funds were received by May 2005. Table 4 shows all the items that were purchased with the funds from the Associated Students Budget as well as donated by Trex Enterprises and Visual Solutions.

Table 4 Budget

Item# Part Part # Quantity Paid by Cost /Unit Total

1 Power Supply (28V 3A) BK 1670A 1 ASB $189 $189 2 Tools (laser, pliers, 1 ASB $270 $270 screwdrivers, cutters, and etc…) 3 Single axis gimbal 1 Trex $200 $200 4 BEI Rotary Actuator RA60-10-014Z 1 Trex $2000 $2000 5 MEMS Gyro ADXRS150EB 6 Trex $75 $450 6 Advance M 1 Trex $500 $500 Linear power amplifier S25A 7 CIO 1 Trex $998 $998 Data acquisition board DAS1602/16 8 Potentiometer P3 4204 1 Trex $20 $20 9 Breakout board for data 1 Trex $70 $70 acquisition board 10 Cable for data 1 Trex $20 $20 acquisition board 11 107uF Capacitors 30 USD $0.25 $7.5 12 Resistors 40 USD $0.10 $4 13 LM337 3 USD $0.25 $0.75 14 LM317 3 USD $0.25 $0.75 15 LM348 9 USD $0.25 $2.25 16 Power Connectors DigiKeyWM464 2 Self $3.68 $7.37 17 Input/output connectors DigiKeyWM4650 2 Self $7.66 $15.32 18 Labor 440 Self $12/hour $5280 19 VisSim Software Real-time pro. 1 Visual $1000 $1000 20 PCB board 2 Trex $115 $230 Trex donations $4113 Visual Solutions $1000 ASB+USD donations $485.0 Total $11264.94

Major components used to build the vibration generator systems: - Single axis gimbal - vibration platform (item 3, Table 3)

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a. +/- 6 degree motion, excellent candidate for the moving platform - Linear power amplifier for current gain (item 6, Table 3) a. Has an option for both the voltage and the current mode b. Used in the current mode to drive the motor - Data acquisition board for virtual components (item 7, Table 3) a. Excellent candidate for digital to analog conversion between real and virtual components b. Very expensive, but provides undeniable reliability - Breakout board for data acquisition board for communication between real and virtual components (item 9, Table 3) a. Used with the data acquisition board - VisSim software provided by Visual Solutions for virtual components (item 19, Table 3) a. Provides real-time simulation b. Very efficient and fast c. Many options for control system analysis - Power Supply (28V 3A) (item 1, Table 3) a. Reliable power supply - BEI Rotary Actuator to move the single axis gimbal (item 4, Table 3) a. +/-6 degrees b. Fast - Potentiometer to track angle change (item 8, Table 3) a. Very cheap b. Easy to use c. An infinite resolution (0-340◦)

Major components used to build the virtual filter: - MEMS Gyro for low frequency vibrations (item 5, Table 3) a. Cheap b. Low frequency, as low as 0.01Hz - Data acquisition board for virtual components (item 7, Table 3) - Breakout board for data acquisition board for communication between real and virtual components (item 9, Table 3) - VisSim software provided by Visual Solutions for virtual components (item 19, Table 3)

Major components used to build the Gfilters, Hfilters and the blending circuitry: - LM348 for the filters and the summing amplifier (item 15, Table 3) LM348 easy to use, cheap and saves space on the PCB board because it has four 741 operational amplifier per chip - LM337 for the -2.5 V reference (item 13, Table 3) LM337 easy to use, previous experience using the chip and free (provided by USD) - LM317 for the 5 V reference (item 14, Table 3) LM317 easy to use, previous experience using the chip and free

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(provided by USD) - Power connectors for the power and the ground supply (item 16, Table3) Cheap, small and universal - Input/output connectors for the blending filter (item 17, Table 3) Cheap, small and universal

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IX Personnel

The YAZ team consists of two personnel. Each person is experienced in a different area of electrical engineering. The basics are understood by both members of the group. The personnel are senior electrical engineering majors at USD. They were chosen by the faculty members to work on this project. The following are the members of the YAZ team: Yoshitaka Yano aka Bob and Zlatko Filipovic aka Z

Yoshitaka Yano demonstrates a broad knowledge in hardware due to experience at ITT (Institute of Technology); therefore his assignments were based on his experience. On the other hand, Zlatko Filipovic demonstrates a broad knowledge in software due to his internship experience for a software company. His assignments were mainly based around software.

The most helpful courses for this project were: Control Systems (for building the vibration generator system), Electronics (for building the blended filter), Microcontrollers (for the PCB layout) and DSP (for decision making between analog and digital design).

Table 5 lists the tasks assigned to each team member.

Table 5 Member’s task list Tasks Zlatko Filipovic Yoshitaka Yano Accomplished

Understand Project x x √ Understand MEMS x √ Understand MHD x √ Design Filter (PSpice) x √ Design Filter (MatLab) x √ Design Filter (Maple) x x √ VisSim Learning x x √ Design of vibration generator x √ system (MatLab) Design of vibration generator x √ system (VisSim) Design of vibration generator x √ system (MathCad) Order parts for Gimbal x x √ Build VGS ( vibration generator x x √ system) using the model Test VGS x x √ Test MEMS x √ Improve VGS x √ Implement H-filter in PSpice x √ Build H-filter circuit x √ Design PCB board/order x √ Test PCB board x x √ Test, build three-axis PCB board x x √ with the complete system

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X Design Schedule

Table 6a and 6b represent the schedule for the first part of this project. Table 6c and 6d represent the schedule for the second part of this project. The first semester (Spring 2005) was devoted to the design of a vibration generator system that generates low frequency vibrations (up to 20 Hz). The second semester (Summer 2005) was dedicated to testing the vibration generator system and building the integrated filter.

The project sponsor was consulted and updated every week. We met Mr.Mike Borrello once a week to discuss the tasks and the steps taken during this project.

Table 6a Gantt chart for this project (week1-week7)

Table 6b Gantt chart for this project (week7-week 15)

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Table 6c Gantt chart for this project (week1-week6)

Table 6d Gantt chart for this project (week7-week 11)

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XI References and Bibliography

Books:

BEI Technologies, Inc. (2005). Rotary Voice Coil Actuators. Retrieved March 16, 2005, from http://www.beikimco.com/products/rotaryvoicecoil.php

P. Lewis and C. Yang. (1997). Basic Control System Engineering. New Jersey: Prentice Hall

M. Kawata, and K. Nishoka. 2001. Control System Made Easy with MATLAB/Simulink. Tokyo: Morikita Publisher

Robbins and Myers. 1975. Motors · Speed Controls · Servo Systems, 3rd ed. Minnesota: Electro-Craft

Robbins and Myers. 1989. Motors · Speed Controls · Servo Systems, 5th ed. Minnesota: Electro-Craft

Trex Enterprises. (2000). Avionics. Retrieved March 16, 2005, from http://www.trexenterprises.com/

T.Shubert and E.Kim 1996. Active and non-linear electronics, Toronto: Jhon Wiely and Sons,Inc.

Internet:

Trex Enterprises, (2000) Avionics, Retrieved March 16, 2005, http://www.trexenterprises.com/

Applied Technology Associates, (2005), Sensors and Actuators http://www.atasensors.com/

Analog Devices, (2005), MEMS and Sensors http://www.analog.com/

MEMS and Nanotechnology Clearinghouse (2005), MEMS devices http://www.memsnet.org

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XII Summary

The goal of this two semester senior design project was to design and implement a filter that will allow two sensors to act as one single sensor that can detect both low and high frequency vibrations due to disturbances. MEMS sensors and MHD sensors are two sensors capable of measuring both low and high frequency vibrations when combined.

The first semester design was dedicated to building and analyzing a vibration generator system that measures very low frequencies using MEMS sensors. This part of the project was strictly dedicated to vibration generator system that is used for testing both high and low frequency sensors. The main goal for the second semester was to use the low frequency measurements from MEMS, generated by the vibration generator system vibrations, along with high frequency measurements (provided to us by ATA), generated by Magneto-Hydro-Dynamic (MHD) sensors, to implement a filter that will allow these sensors to act as one single sensor.

Using the MEMS’s and MHD’s transfer functions (TF) and the synthesis method (TFMHDxGfilter + TFMEMSxHfilter = TFBLEND) the blended output was obtained. The synthesis method produced a third order Hfilter and a unity gain Gfilter which were implemented and built. Implementing these two filters, along with the blending circuitry for MEMS and MHD, on a PCB board a new sensor capable of measuring both low and high frequency vibrations, from about 0.01 Hz to 1000 Hz, was created. Although the sensor was designed to measure frequencies up to 1000 Hz, the actual measurements were only preformed up to 20 Hz due to the vibration generator’s mechanical limits. The new blended sensor preformed with average 90% accuracy.

The final product was delivered to Trex Enterprises on August 12, 2005. The deliverables were a simulation and a piece of hardware. The simulation was hardware in the loop simulation demonstrating blending of the MEMS and MHD sensors and the wide range for vibration detection. The demonstration was executed on the single axis gimbal. The vibration generator system generated low and high frequency vibrations (0.01-20 Hz) that were measured using the final product. Experimental data (such as Figure 16) along with frequency response was provided to prove that the product can cover these frequencies. The final product consists of three filters on a PCB board and three channels of independent circuitry for blending the outputs. The three filters correspond to the three orthogonal axes required by MHD sensors. The blended outputs will cover a wide range of frequencies from 0.01 Hz-1000 Hz.

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Appendix 1 Simulink Simulations

Figure 1 Vibration generator system

Figure 2 Simulated Output with real time measurements generated by VisSim (Vin=1.25) Blue=Step input, Red=Output, Green= Sampled Data from VisSim

Figure 3 Code to generate the plot in Figure 2

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Appendix 2 VisSim Simulations

Figure 1 Vibration generator system (square wave as an input)

Figure 2 Vibration generator system with (square wave as an input) and MEMS output (brown)

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Figure 3 Vibration generator system (step input) 0.15V input: from 0 to 0.15 V

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Appendix 3 Frequency response for YZ axes and VisSim Results

Figure 1 Y-axis: Upper Left: Simulated blended frequency response (pink), MHD frequency response (red) and MEMS frequency response (blue) Lower Right: Hfilter’s frequency response (black) and Simulated blended frequency response (pink)

Figure 2 Z-axis: Upper Left: Simulated blended frequency response (pink), MHD frequency response (red) and MEMS frequency response (blue) Lower Right: Hfilter’s frequency response (black) and Simulated blended frequency response (pink)

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Figure 3 Block diagram for the blended system and the output at 0.1Hz (VisSim)

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Appendix 4 Vibration measurements

Vibration Measuerements (Z-axis)

7

y = 0.3481x 6

5

4

3 Rate(rad/sec) 2

1

0 0 2 4 6 8 10 12 14 16 18 Frequency (Hz)

Blend Mems MHD PotRate Linear (PotRate)

Figure 1 Z-axis vibration measurements

Vibration Measurements

7

6 y = 0.3331x

5

4

3 Rate (rad/sec) Rate 2

1

0 0 2 4 6 8 10 12 14 16 18 Frequency (Hz)

Blend Mem s MHD PotRate Linear (PotRate)

Figure 2 Y-axis vibration measurements

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Appendix 5 PCB layout and Schematics

Figure 1 PCB Layout of the complete system

Figure 2 XYZ Hfilters

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Figure 3 Gfilers and the blending circuitry

Figure 4 MEMS offset and the voltage reference

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Appendix 6 User’s manual

User’s Manual

PCB Board Instructions

ELEC 492

Updated: August 03, 2005

August 12, 2005 University of San Diego

Prepared by: Yoshitaka Yano Zlatko Filipovic

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Figure 1 PCB Layout

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Note: In Figure 1: 1.) red fonts indicate the inputs to the PCB board 2.) blue fonts indicate the outputs from the PCB board

I Connectors There are two PCB connectors, a three pin connectors and a twelve pin connectors.

3 Pin Connector (Connector - Molex, .156 in KK, rt ang, 3 pin (DigiKeyWM4641)) This connector is the power supply connector and it requires +/- 15 V DC power supply.

To use this connector do the following: 1. Connect +15V to Vcc+ input pin 1 2. Connect -15V to Vcc- input pin 2 (middle pin) 3. Connect the ground to GND pin 3

12 Pin Connector (Connector - Molex, .156 in KK, rt ang, 12 pin (DigiKeyWM4650)) This connector is used for: - X,Y and Z MEMS inputs - X,Y and Z MHD inputs - X,Y and Z Blended Outputs - + 5V output to MEMS - +15V output to MEMS - Extra ground used as ground to MEMS and MHD

To use this connector do the following: 1. Carefully connect the X,Y and Z outputs from MHD to pins 12 (X), 11 (Y), 10 (Z) 2. Carefully connect the X,Y and Z outputs from MEMS to pins 9 (X), 8 (Y), 7 (Z) 3. Connect the blended outputs of X (pin 6), Y (pin 5), and Z (pin 4) to a measurement device such as: oscilloscope, VisSim, etc. 4. Connect +15V DC(pin 2), and 5V DC (pin 1) to the corresponding pins of MEMS.

II Potentiometers There are two potentiometers located on the PCB board:

Potentiometer 1 (as indicated in Figure 1) This pot is used to accurately set the voltage reference of 5V required by MEMS.

To adjust the 5V voltage reference, connect pin 1 (output) to a DMM (Digital Multi- Meter) and rotate the potentiometer until the output is tuned to 5V.

Potentiometer 2 (as indicated in Figure 1) This pot is used to accurately set the voltage reference of -2.5V required to offset the MEMS.

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To adjust the -2.5V voltage reference, connect pin 3 (output) of the LM337 regulator to a DMM (Digital Multi-Meter) and rotate the potentiometer until the output is tuned to - 2.5V.

Note: The potentiometers are calibrated and they should not be changed unless necessary.

III Jumpers The connectors at jumpers X, Y, or Z are used to make MEMS output (InMEMSX, InMEMSY, or InMEMSZ) produce either positive voltage or negative voltage (Figure 2).

Figure 2 -2.5V offset with jumpers

MEMS produces positive voltage output for the clockwise rotation around the axis which is normal to the top of the MEMS package as shown in Figure 3 (www.analog.com).

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Figure 3 MEMS directional rotation

Make jumper connection between a pin1 and pin2 at jumper X, Y, or Z: By connecting pin 1 and pin 2, blended outputs of the summing amplifier (inverting amplifier), are connected to the inverting amplifiers that follow. It makes the InMEMSX, InMEMSY, or InMEMSZ produce a positive voltage output for the clockwise rotation.

Make jumper connection between a pin1 and pin3 at jumper X, Y, or Z: By connecting pin 1 and pin 3, blended outputs of the summing amplifier (inverting amplifier), are not connected to the inverting amplifiers that follow. It makes the InMEMSX, InMEMSY, or InMEMSZ produce a positive voltage output for the counterclockwise rotation.

Note: Do not connect pin 2 and 3. Pin 4 is not used. If you make a jumper connection between pin 2 and 3, the path to the blended output will be an open circuit. Pin 4 is not connected to anywhere.

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Appendix 7 PSpice Simulations of Hfilter

Figure 1 X-axis frequency response in PSpice

Figure 2 H x-axis filter design

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