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Team2_Final_Project_Documentation

This document describes a student project to design an emergency braking system for a Hyperloop pod. The system uses a stepper motor mechanism to apply a controlled clamping force on a force sensor. The force values are sent to MATLAB via a microcontroller for visualization. The goals were to control the clamping force and stop it at a specified force value. While most functionalities worked individually, integrating them proved challenging within time constraints. Potential improvements include optimizing the clamping mechanism and simulating electrical failure with a switch.

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1 Names: Tristan Roberts and Jacob Grendahl Project Title: Hyperloop Pod Emergency Brake Team Number: Team 2 Project Dates: April 1, 2016 to May 6, 2016 Problem Description: A Hyperloop pod design is meant to be a marketable product, so safety is of paramount importance. We are members of the SpaceX Hyperloop Competition Club, and we’ve explored different options to bring the pod to a controlled stop. Our primary braking method is implemented by reversing the polarity of a linear accelerator, which is an entirely electrical system. However, our design needs to be fail-safe and account for potential emergencies. Therefore, another braking system needs to be in place to account for a loss of electrical power. The application of our final project is a control system for the emergency braking system of our team’s Hyperloop pod design. Our system is triggered when the primary braking system cuts out, and it brings the pod to a controlled stop through friction by clamping a guide rail. We mimicked this situation by using a stepper motor system to exert a controlled clamping force on a force sensor. Project Objectives: Our primary objective was to create a mechanism that exerted a controlled, measurable force on a force sensor. We wanted to record the force data over time in MATLAB so we could visualize the strength and consistency of the clamping force. Ideally, we also wanted to have an external interrupt (e.g. a loss in electrical power, simulated by a switch) trigger the clamping motion. Eventually, we also would have wanted the mechanism to clamp to an optimal force value based on the pod’s acceleration, measured by an accelerometer. Motivation for Topic: Our motivation for this topic comes from us both being members of the SpaceX Hyperloop Competition Team. For a design weekend at Texas A&M in January, our team designed multiple subsystems of a Hyperloop pod, receiving great feedback from judges and peers. Our club is still extremely interested in the concept, so we plan to design and build a full pod design for a potential competition next year. This Mechatronics project is one small step towards that goal, because as a club we know we want to utilize a friction-based emergency braking system. As a team, we intend to continue work on the emergency brake concept outside of this class to produce a working model for use on both test-scale and full-scale pods. Desired Requirements:  Our microcontroller will sense the response of a force sensor through analog-to-digital conversion.  The values we extract from the force sensor will be converted to a useful form (e.g. Newtons).  A plot of force over time from the force sensor will be displayed in MATLAB.  The plot in MATLAB will be continuously updated as time progresses.  Any inaccuracies due to noise will be minimized through data filtering.  The stepper motor system will cause a clamping force on the force sensor.
2  By altering the input to the stepper motor, we will dynamically change the force applied to the force sensor.  We will stop the mechanism from clamping once it reaches a specified force value.  The clamping force will be initiated using an external interrupt (a switch).  A relationship will be established between acceleration and the ideal clamping force.  The response of an accelerometer will cause the mechanism to exert the ideal clamping force. Plan of Execution: The goals we had, as described in the “Project Objectives” section, each required many smaller developments. The steps of development for our project are detailed in the following table: Project Functionalities Implementation Order MCU Functionality Details of Project Task Project Functionality Percent of Project Complete? 1 Input/Output, Analog/Digital, LCD (for testing) Measure the response/value of a force sensor Display force data over time in MATLAB 15 X 2 USB to TTL Serial Communication, Input/Output Transfer the force values to MATLAB 15 X 3 Analog/Digital, Mathematics Convert the output of the force sensor to a useful unit (e.g. Newtons) 10 X 4 Timers, Mathematics Plot the force data over time 10 X 5 Pulse Width Modulation, Input/Output Control a stepper motor using PWM Exert controlled clamping (braking) force to stop the pod comfortably 20 X 6 Hardware Create a system to exert a clamping force on the sensor 20 X 7 External Interrupts, Input/Output Use a switch to cause an external interrupt in the PIC16F690 Sense when electrical braking system cuts out 3 8 External Interrupts, Input/Output Trigger the response of the stepper motor using a switch 2 9 Input/Output, Analog/Digital Measure the response of an accelerometer Clamping force responds to the amount of acceleration 3 10 Mathematics Control the clamping force with the accelerometer 2
3 We were able to complete six out of our ten desired functionalities, which accounted for 90% of our project. We had planned for the last four functionalities to be extra features that we would try to get working if we had time. The operation of our mechanism is detailed in the following chart: Our microcontroller was connected to MATLAB through a USB to TTL serial connection. When our circuit was powered on and the MATLAB program was run, our microcontroller caused the stepper motor to step continuously. The stepper motor was directly connected to our Lego gear mechanism. Our mechanism caused two lever arms to clamp together tighter with each step of the stepper motor. Our force vs. time plot updated continuously for each sample, and the program terminated after a specified number of data samples. The gray boxes show functionalities that we started on, but that we couldn’t working for the final design. We left the code for these functionalities in our final ASSEMBLY code, but the sections are commented out. Throughout the course of the project, almost the entirety of the work was collaborative. We often had one person working on the physical circuit while the other person worked on programming. However, we consistently switched who was performing which role. Additionally, we would always debug each other’s code and both look at the circuit to make sure everything was set up correctly. We felt like this was the best way to approach this project because it guaranteed that both of us had a full understanding of what the other was doing, which made working through roadblocks significantly easier.
4 Parts List: Parts List Product Name Quantity Manufacturer Manufacturer Part Number Vendor Vendor Product Code PIC16F690 Microcontroller 1 Microchip PIC16F690 Microchip PIC16F690 PICKIT 3 Programmer 1 Microchip PG164130 Microchip PG164130 PIC Programming Socket – X55X Series 1 ARIES Electronics 28-6554-10 Digi-Key A302-ND Laptop w/ MATLAB & MPLABX Software 1 N/A N/A N/A N/A Voltage Source 1 Elenco XP-581A Elenco XP-581A Stepper Motor Controller 1 Texas Instruments DRV8825, md20b Pololu 2133 Stepper Motor 1 Pololu SY35ST28- 0504A Pololu 1208 FSR Force Sensor 1 Interlink Electronics 30-81794 Digi-Key 1027-1001-ND Lego Technic Set – Gears, Axles, Shafts 1 Lego N/A Lego Education N/A Switch 1 C & K Components JS202011SCQN Digi-Key 401-2002-1- ND 3-Axis Accelerometer 1 Pololu MMA7341LC Pololu 1247 Liquid Crystal Display 1 Lumex Opto/Components Inc. LCM- S01602DSR/B Digi-Key 67-1769-ND USB to TTL Serial Connection Cable 1 FTDI Chip TTL-232R-5V FTDI Chip TTL-232R-5V USB 2.0 to Mini- USB Cable 1 Qualtek 3021003-03 Digi-Key Q362-ND 5V Voltage Regulator 1 Texas Instruments 296-13996-5- ND Digi-Key 296-13996-5- ND Resistor, 3kΩ 1 Stackpole Electronics Inc. CF14JT3K00 Digi-Key CF14JT3K00TR- ND Capacitor, 220μF 1 Nichicon UVZ0J221MDD Mouser Electronics 647- UVZ0J221MDD Large Bread Board 1 PROAM 509-020 PROAM 509-020 Small Bread Board 1 PROAM 509-005 PROAM 509-005 Wire Kit 1 Elenco JW-350 Elenco JW-350 2-Pin Banana Cables 3 Pomona Electronics B-4-0 Digi-Key 501-1328-ND Long Pin-Out Strip 1 SparkFun 116 SparkFun 116
5 Hardware Design: Our hardware setup is detailed in the following diagram: The hardware diagram shows the how all of the interactions between our circuit, microcontroller and mechanism work. Any arrows going out of a component represent outputs, and any arrows going into a component represent inputs. The clamping mechanism we designed is shown below:
6 The mechanism shown here was built using Lego gears, shafts and other various parts as a very rough prototype for the clamping mechanism that would be used on the Hyperloop pod build. This was more of a proof of concept than a mechanism that would actually be used. One key feature of this mechanism are the gears connected to the stepper motor that transfer the force from one shaft to another. The other key feature is the two clamping arms connected to adjoining gears through their shafts. Electronic Circuit Design: Our circuit used to test our first functionality is shown below: This circuit was used as a proof of concept more than anything. The LCD was used to display the decimal values recorded from the analog to digital conversion of the force sensor. Once we proved we could correctly measure the force values, we disassembled the circuit and moved to sending values to MATLAB through use of a COM port.
7 Our final circuit for the project is shown below: This circuit was used to take analog readings from a force sensor and send the digital equivalent to MATLAB. The other functionality of this circuit was to start and stop a stepper motor when the microcontroller determined it was a good time to do so. Our microcontroller was configured to take inputs from the switch and force sensor. The receive pin is connected to MATLAB through the use of a TTL adapter, as shown. It was also configured to output to the driver of the stepper motor and to the transmit pin connected to MATLAB. The driver of the stepper motor was connected to a 12V source with a 5V logic input from the microcontroller. The 12V power supply was connected to the ground through a 220μF capacitor for protection. Four of the pins provided output to the stepper motor and controlled its movements. The transmit and receive pins of the microcontroller were connected to a TTL adapter so they could be connected to a computer. Power and ground were also connected to this adapter so the computer would know a device was connected. All components that required 5V were supplied 5V through use of a voltage regulator. This provided protection in case a 5V power supply was not available.
8 Programming: The microcontroller we selected was the PIC16F690. We selected this particular microcontroller due its ability to perform analog to digital conversion and its high number of pins for input and output. The pseudo code below outlines the general goals for our microcontroller ASSEMBLY program:
9 Our detailed ASSEMBLY code is shown below:
10 The program utilized four major microcontrolling categories (analog to digital conversion (ADC), pseudo pulse width modulation (PWM), RS232 communication, and input/output). The input and output was primarily used to check whether or not the switch had failed and to take analog input from a force sensor (shown in the “Power” subroutine). The pseudo PWM was used to control the stepper motor. This was implemented by pulsing the step pin on the stepper motor driver at intervals determined by a delay loop. We decided to use this because it was easier to implement in the limited lab time so we could attempt to complete more of our functionalities (shown in “Step” subroutine). The RS232 was used to communicate with MATLAB and was implemented using the transmit and receive registers on the microcontroller (shown in SendW subroutine). The ADC was used to convert the voltage input from the force sensor to digital values that could be stored, analyzed and later transmitted to MATLAB for analysis (shown in the “ADC” subroutine).
11 Our MATLAB code is detailed in the diagram below:
12 The MATLAB portion of the code follows the pattern of the diagram shown above. It takes inputs coming from the microcontroller and converts the digital values to voltages, and then to force values. The conversion from voltage to force was done by creating an equation through the use of regression. Known points were read from the Voltage vs. Force diagram (shown below) in the force sensor datasheet. These points were converted into log-log form for the curve fitting. When the fitting was complete, the equation was converted back to the non-linear form to be used by the main loop. The plot we used to perform our regression analysis is shown below: In the voltage divider circuit, a 3kΩ resistor was used for RM; this is because we desired the shallowest curve for more accuracy when using smaller force values. Testing/Proof of Operation/Conclusion: In reality, certain components of our project work very well, but we could not get them all to work in unison. For example, our live plot in MATLAB works extremely well as someone squeezes the force sensor with their fingers. The low-pass filter allows the force diagram to be almost entirely smooth with no noticeable noise. Also, as we run the MATLAB program, the stepper motor steps at a good rate and the lever arms clamp together. However, we could not get our clamping mechanism to produce a high enough force to be recognized by the sensor. This is because the mechanism wasn’t very robust; one of us had to fix the position of the mechanism and stepper motor to keep them from rotating with the lever arms. Another thing that contributed to this was that the surface between the two lever arms did not provide a good enough clamping surface to be recognized by the force sensor. The only other remaining bugs from our main goals are the switch not working and the motor not stopping when the selected force value is applied. In the current state of the project, when the circuit is plugged into a 5V and 12V supply, there should be no moving components, but the stepper motor should hum. When the MATLAB program is run, the stepper motor should start rotating at a consistent speed, and a plot should appear on the screen of the computer. If the force sensor is squeezed, the live updating plot should show an accurate representation of how the sensor was squeezed.
13 An example of one of our Force vs. Time plots is shown below: Potential Improvements/Future Work: Although we were able to accomplish a lot over a short time period, there is a lot more work to be done with our project. Some of the things we would like to accomplish in the future are:  We would like to compare the results from our stepper motor mechanism to the results we would get from a solenoid to see which provides a more consistent clamping force on the sensor. The reason we weren’t able to complete this is that the time constraints did not allow for enough time to to research and order a proper solenoid for the project.  It would be great to build a more robust clamping mechanism to minimize fluctuations and inaccuracies in the force data. We had trouble with the fact that our mechanism wasn’t
14 squeezing the force sensor as tightly as we wanted, so we think a better design could remedy some of our major issues.  We need to simulate an electrical failure using a switch. We were close to getting this functionality working before the project deadline, so we would just need to debug our code further to achieve this.  Eventually, our ultimate goal is to clamp to an optimal force value based on the pod’s acceleration, which we want to mimic with an accelerometer. This would allow our pod design to reach a controlled and comfortable stop.  We would like to research clamping materials to get an optimal coefficient of friction for use on a Hyperloop pod.  After all our functionalities are complete, we would like to test our idea using a small-scale version of our Hyperloop pod design. Troubleshooting: One difficulty that we had with the project was trying to get the stepper motor to stop stepping after reaching a certain force value. It seemed like we had the logic correct, but a minor error in the code or wiring may have caused it to malfunction. Another issue we had was using the switch to trigger the response of the stepper motor. For some reason, we couldn’t get the port to recognize when the switch was flipped. When troubleshooting earlier parts of the project, commenting out specific sections or lines of code were useful for evaluating which parts of the code were actually working. Also, when applicable, it really helped us to use the debugging tool in MPLABX. What We Have Learned: This project was our first exposure to controls and the first place that we could apply our knowledge of circuits in a practical way. What we would like to take away from this project and apply to our careers is the ability to take a very complex project, and break it into many simple functionalities. By utilizing the information taught to us during lecture and looking through data sheets for our requested components, we were able to work our way through numerous challenges presented by our choice of project. Theoretical topics such as 8-bit and 10-bit mathematics were vital for our functionalities, so learning that material during lecture really aided us in practice.
15 Appendices: ASSEMBLY Code – Team2_Final_Project.asm: ;Authors: Jacob Grendahl, Tristan Roberts ;Date: May 6, 2016 ;Class: AME 487 ;Assignment: Final Project ;File: Team2_Final_Project.asm ; ;Description: ; This is meant to program a PIC16F690 ; The controller is supposed to control an emergency braking system ; through use of analog input from a force sensor, and output to a stepper motor. ; When matlab begins to listen and power failure has been simulated, the stepper ; motor should begin to step. ; ; When the optimal force value is reached, the stepper motor should stop stepping. ; The controller should be sending the digital force values to matlab indefinitely. List P=16f690 #include <p16f690.inc> ;Codeprotect on, watchdog off, internal high speed osc, powerup timer on, clear reset off, brown out off __CONFIG _CP_ON & _WDT_OFF & _INTOSCIO & _PWRTE_ON & _MCLRE_OFF & _BOR_OFF CBLOCK 0x20 temp num Dlay Period OutputVal Check CheckH ENDC org 0x00 goto start ;***************************************************; ;Initialize Oscillator, 8MHz internal ;***************************************************; start ; ADC & MATLAB Setup bsf STATUS, RP0 ; switch to Bank 1 MOVLW b'01110000' ; Set internal oscillator frequency to 8 MHz MOVWF OSCCON
16 bcf STATUS, RP0 ; Switch to Bank 0 clrf PORTC clrf PORTB clrf PORTA bsf STATUS,RP1 ; bank 2 BSF STATUS,RP0 ; Bank 1 clrf TRISC bsf TRISB,RB5 ;set RB5 as input to RX from RS232 BCF STATUS,RP0 ; Bank 0 BCF STATUS,RP1 ; BANKSEL ADCON0 movlw b'10000001' ;Right justify and start ADC unit MOVWF ADCON0 BSF STATUS,RP0 ; Bank 1 movlw b'00110000' MOVWF ADCON1 ;configure ADC unit bsf STATUS, RP1 ; Bank 3 BSF TRISA,0 ; Set RA0 to input BSF TRISA,1 ; Set RA1 to input BCF TRISB,4 ; set RB4 as output BCF TRISB,6 ; set RB6 as output BCF STATUS,RP0 ; Bank 2 BSF ANSEL,0 ; Set RA0 to analog BCF ANSEL,1 ; Set RA1 to digital BCF ANSELH,2 ; set RB4 as digital BCF ANSELH,3 ; set RB5 as digital BCF STATUS, RP1 ; bank 0 ; Stepper Motor Setup movlw 1 << 2 ; Start with Bit 2 Active movwf PORTC movlw 7 ; Turn off Comparators movwf CM1CON0 movlw b'00000011' ; RC5:RC2 are Outputs banksel TRISC movwf TRISC bcf STATUS, RP0 ; Return Execution to Bank 0 movlw 1 << 2 ; Initialize the Output Bit movwf OutputVal
17 call SetUpRS232 ; the following segment waits for a external command (128) recd by RS232 ; then sends back the value of the ADC storred in Speed ; RB5 is RX for RS232 and also external interrupt on port change ; RB7 TX transmit ;call Init_SPI ;Set RA0 for analog input BCF STATUS,RP1 BCF STATUS,RP0 ; Bank 0 BANKSEL ADCON0 movlw b'10000001' MOVWF ADCON0 BSF STATUS,RP0 ; Bank 1 movlw b'00110000' MOVWF ADCON1 bsf STATUS, RP1 ; Bank 3 BSF TRISA,0 ; Set RA0 to input BCF STATUS,RP0 ; Bank 2 BSF ANSEL,0 ; Set RA0 to analog ;***************************************************; ; Check 128 ; ;***************************************************; Check128 ; enable receiver banksel RCSTA bsf RCSTA, CREN ; wait until a byte has been received btfss PIR1,RCIF goto $-1 movf RCREG,w ; send name if rcvd char is 128 sublw .128 btfsc STATUS,Z goto Power goto Check128 ;***************************************************; ; Set up RS232 ; ;***************************************************;
18 SetUpRS232 ;Initialize the transmitter BANKSEL TXSTA ;Goto Bank 1 BCF TXSTA, SYNC ;Asynch mode BSF TXSTA, TXEN BSF TXSTA, BRGH ;19.2k 8MHz BCF BAUDCTL, BRG16 ;19.2k 8MHz ; BSF TXSTA,TX9 ;enable 9-bit transmission (stop bit) ; BCF TXSTA,TX9D ;stop bit is set to 1 MOVLW 0x19 ;19.2k 8MHz MOVWF SPBRG ;19.2k 8MHz BANKSEL RCSTA ;Bank 0 BSF RCSTA, SPEN ;Enable serial port RETURN ;***************************************************; ; Power Failure ; ;***************************************************; Power ; btfss PORTA,1 ; is power still on? ; goto Power ; Yes movlw b'00000000' ;Initialize Check movwf Check goto Loop ; NO ;***************************************************; ; Loop ; ;***************************************************; Loop call ADC ;Gather force data call check btfss Check,0 ;Continue Stepping? call Step ;Yes movfw ADRESH andlw b'00000011' ;ensure data is clean (no bad data) call SendW ;send high force movfw ADRESL call SendW ;send low force goto Loop ;***************************************************; ; Analog to Digital Conversion ;
19 ;***************************************************; ADC movlw 5 ; Wait some usecs for ADC to Charge addlw 0x0FF ; Take One Away to Setup the Charge btfss STATUS,Z ; Check the zero bit goto $-2 bcf STATUS, RP0 bcf STATUS, RP1 ; Bank 0 BSF ADCON0,GO ; Start conversion BTFSC ADCON0,GO ; Is conversion done? GOTO $-1 ; No, test again return ;***************************************************; ; Check ; ;***************************************************; check btfss Check,0 ;checks for already being stopped goto run BANKSEL PORTC clrf PORTC BANKSEL TRISC bsf TRISC,2 BANKSEL PORTC return run bcf STATUS,C ;movlw b'00000010' ;High bits for binary 517 ;movwf CheckH movlw b'11110001' ;low bits for binary 517 addwf ADRESL,w ;start of 10 bit addition btfsc STATUS,C bsf Check,0 ;incf CheckH ;if low bit overflow increment ;movfw ADRESH ;andlw b'00000011' ;addwf CheckH,f ;check high order bits ;btfsc CheckH,2 ; incf Check ;if high order "overflow" set check return
20 ;***************************************************; ; Step ; ;***************************************************; Step BANKSEL PORTC movlw d'230' movwf Period movlw 0x80 ; Forwards or Reverse? subwf Period, w Forwards: ; Move Stepper Forwards xorlw 0x7F ; Negate the Value for Delay movwf Period rlf OutputVal, w ; Shift the Saved Value andlw b'00111100' btfsc PORTC, 5 ; Roll Over? iorlw 1 << 2 movwf PORTC movwf OutputVal ; Save New Set Bit DlayLoop: ; Repeat Delay Loop for "Period" movlw HIGH ((1000 / 5) + 256) movwf Dlay movlw d'25' addlw -1 btfsc STATUS, Z decfsz Dlay, f goto $ - 3 decfsz Period, f goto DlayLoop return ;***************************************************; ; Send Work Register ; ;***************************************************; SendW ;check status of transmit bit, wait until set BANKSEL TXSTA BTFSS TXSTA, TRMT GOTO $-1 BANKSEL PIR1 BTFSS PIR1, TXIF GOTO $-1
21 BANKSEL TXSTA BSF TXSTA,TX9D ;stop bit is set to 1 ;Load working register into TXREG BANKSEL TXREG MOVWF TXREG ;Wait until character is sent BANKSEL TXSTA BTFSS TXSTA, TRMT GOTO $-1 skipsend RETURN END
22 MATLAB Code – ForceConversion.m: %Names: Jacob Grendahl, Tristan Roberts %Date: May 6, 2016 %Class: AME 487 %Assignment: Final Project %File: ForceConversion.m % %Description: % This file is responsible for converting the binary bits recieved % into force values. This is achieved by first creating an equation % that converts voltage to force, then running through the main loop. % The main loop constantly times the conversions and updates a force vs % time plot. out=instrfind(); delete(out); clc;clear; run('Regression'); s = serial('COM6'); %Serial port configuration set(s,'BaudRate',19200); set(s,'InputBufferSize',2); %-------------------------------------------------------------------------- fopen(s) %Open serial port N = 500; fwrite(s,128,'async') %Send interupt signal to the microcontroller ii=2; t(1)=0; while ii<=N tic out(ii,1) = fread(s,1,'uint8'); %Read data from the input buffer switch out(ii,1) case 3 out(ii,1)=2^9+2^8; case 2 out(ii,1)=2^9; case 1 out(ii,1)=2^8; case 0 out(ii,1)=0; otherwise out=out(1:ii-1,:); continue end out(ii,2) = fread(s,1,'uint8'); %Read data from the input buffer b=toc; t(ii)=t(ii-1)+b; Vout(ii)=(out(ii,1)+out(ii,2))/1024*5; %DAC for voltage readout F(ii)=Func(Vout(ii)); F(ii)=lowpassfilter(F(ii-1),F(ii)); plot(t(1:ii),F(1:ii),'--k');
23 drawnow xlabel('Time (s)'); ylabel('Force (N)'); title('Force vs. Time'); ii=ii+1; end %-------------------------------------------------------------------------- fclose(s) %Close serial port delete(s) clear s
24 MATLAB Code – lowpassfilter.m: %Names: Jacob Grendahl, Tristan Roberts %Date: May 6, 2016 %Class: AME 487 %Assignment: Final Project %File: lowpassfilter.m % %Description: % This file removes noise from the force values that are taken function F=lowpassfilter(F0,F1) F=0.5*F0+0.5*F1; end
25 MATLAB Code – Regression.m: %Names: Jacob Grendahl, Tristan Roberts %Date: May 6, 2016 %Class: AME 487 %Assignment: Final Project %File: Regression.m % %Description: % This file is resopisible for building the equation that converts % voltage to force values. F=9.8/1000*[20 50 95 195 310 440 570 705 900 1000]; V=[0.35 0.5 0.7 1 1.2 1.45 1.625 1.8 1.95 2]; X=log(V); Y=log(F); Z=[ones(length(V),1) X']; A=Z'*Z; b=Z'*Y'; a=Ab; x=0:0.1:5; y=exp(a(1)).*x.^a(2); Func=@(x)exp(a(1)).*x.^a(2); plot(V,F,'or',x,y,'-k'); xlabel('Voltage Out (V)'); ylabel('Force (N)'); title('Force vs. Voltage Output');
26 The necessary data sheets required to complete this project are attached in a separate folder labeled “Appendices.” The included data sheets are as follows:  PIC16F690, Microchip  FSR Force Sensor, Interlink Electronics  SY35ST28-0504A Stepper Motor, Pololu  DRV8825 Stepper Motor Controller, Texas Instruments A lot of the information we used about the stepper motor and stepper motor controller came from the following links:  Stepper Motor: https://www.pololu.com/product/1208/resources  Stepper Motor Controller: https://www.pololu.com/product/2133
27 Works Cited DRV8825 Stepper Motor Driver Carrier, High Current. Tech. Pololu, n.d. Web. 28 Apr. 2016. FSR Integration Guide. Tech. Interlink Electronics, n.d. PDF. 28 Apr. 2016. Hyperloop Alpha. Tech. SpaceX, 12 Aug. 2013. PDF. 28 Apr. 2016. Hyperloop Braking System Render. Digital image. Delft Hyperloop. Mkb Brandstof, 22 Jan. 2016. Web. 28 Apr. 2016. PIC16F690 Data Sheet. Tech. Microchip, n.d. PDF. 28 Apr. 2016. SY35ST28-0504A Stepper Motor Data Sheet. Tech. Pololu, n.d. PDF. 28 Apr. 2016. The University of Arizona Air Bearings & Suspension Hyperloop Pod Subsystem Design. Tech. Tucson: The University of Arizona Hyperloop Competition Team, 28 Jan. 2016. PPT. 28 Apr. 2016.

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Team2_Final_Project_Documentation

  • 1.
    1 Names: Tristan Robertsand Jacob Grendahl Project Title: Hyperloop Pod Emergency Brake Team Number: Team 2 Project Dates: April 1, 2016 to May 6, 2016 Problem Description: A Hyperloop pod design is meant to be a marketable product, so safety is of paramount importance. We are members of the SpaceX Hyperloop Competition Club, and we’ve explored different options to bring the pod to a controlled stop. Our primary braking method is implemented by reversing the polarity of a linear accelerator, which is an entirely electrical system. However, our design needs to be fail-safe and account for potential emergencies. Therefore, another braking system needs to be in place to account for a loss of electrical power. The application of our final project is a control system for the emergency braking system of our team’s Hyperloop pod design. Our system is triggered when the primary braking system cuts out, and it brings the pod to a controlled stop through friction by clamping a guide rail. We mimicked this situation by using a stepper motor system to exert a controlled clamping force on a force sensor. Project Objectives: Our primary objective was to create a mechanism that exerted a controlled, measurable force on a force sensor. We wanted to record the force data over time in MATLAB so we could visualize the strength and consistency of the clamping force. Ideally, we also wanted to have an external interrupt (e.g. a loss in electrical power, simulated by a switch) trigger the clamping motion. Eventually, we also would have wanted the mechanism to clamp to an optimal force value based on the pod’s acceleration, measured by an accelerometer. Motivation for Topic: Our motivation for this topic comes from us both being members of the SpaceX Hyperloop Competition Team. For a design weekend at Texas A&M in January, our team designed multiple subsystems of a Hyperloop pod, receiving great feedback from judges and peers. Our club is still extremely interested in the concept, so we plan to design and build a full pod design for a potential competition next year. This Mechatronics project is one small step towards that goal, because as a club we know we want to utilize a friction-based emergency braking system. As a team, we intend to continue work on the emergency brake concept outside of this class to produce a working model for use on both test-scale and full-scale pods. Desired Requirements:  Our microcontroller will sense the response of a force sensor through analog-to-digital conversion.  The values we extract from the force sensor will be converted to a useful form (e.g. Newtons).  A plot of force over time from the force sensor will be displayed in MATLAB.  The plot in MATLAB will be continuously updated as time progresses.  Any inaccuracies due to noise will be minimized through data filtering.  The stepper motor system will cause a clamping force on the force sensor.
  • 2.
    2  By alteringthe input to the stepper motor, we will dynamically change the force applied to the force sensor.  We will stop the mechanism from clamping once it reaches a specified force value.  The clamping force will be initiated using an external interrupt (a switch).  A relationship will be established between acceleration and the ideal clamping force.  The response of an accelerometer will cause the mechanism to exert the ideal clamping force. Plan of Execution: The goals we had, as described in the “Project Objectives” section, each required many smaller developments. The steps of development for our project are detailed in the following table: Project Functionalities Implementation Order MCU Functionality Details of Project Task Project Functionality Percent of Project Complete? 1 Input/Output, Analog/Digital, LCD (for testing) Measure the response/value of a force sensor Display force data over time in MATLAB 15 X 2 USB to TTL Serial Communication, Input/Output Transfer the force values to MATLAB 15 X 3 Analog/Digital, Mathematics Convert the output of the force sensor to a useful unit (e.g. Newtons) 10 X 4 Timers, Mathematics Plot the force data over time 10 X 5 Pulse Width Modulation, Input/Output Control a stepper motor using PWM Exert controlled clamping (braking) force to stop the pod comfortably 20 X 6 Hardware Create a system to exert a clamping force on the sensor 20 X 7 External Interrupts, Input/Output Use a switch to cause an external interrupt in the PIC16F690 Sense when electrical braking system cuts out 3 8 External Interrupts, Input/Output Trigger the response of the stepper motor using a switch 2 9 Input/Output, Analog/Digital Measure the response of an accelerometer Clamping force responds to the amount of acceleration 3 10 Mathematics Control the clamping force with the accelerometer 2
  • 3.
    3 We were ableto complete six out of our ten desired functionalities, which accounted for 90% of our project. We had planned for the last four functionalities to be extra features that we would try to get working if we had time. The operation of our mechanism is detailed in the following chart: Our microcontroller was connected to MATLAB through a USB to TTL serial connection. When our circuit was powered on and the MATLAB program was run, our microcontroller caused the stepper motor to step continuously. The stepper motor was directly connected to our Lego gear mechanism. Our mechanism caused two lever arms to clamp together tighter with each step of the stepper motor. Our force vs. time plot updated continuously for each sample, and the program terminated after a specified number of data samples. The gray boxes show functionalities that we started on, but that we couldn’t working for the final design. We left the code for these functionalities in our final ASSEMBLY code, but the sections are commented out. Throughout the course of the project, almost the entirety of the work was collaborative. We often had one person working on the physical circuit while the other person worked on programming. However, we consistently switched who was performing which role. Additionally, we would always debug each other’s code and both look at the circuit to make sure everything was set up correctly. We felt like this was the best way to approach this project because it guaranteed that both of us had a full understanding of what the other was doing, which made working through roadblocks significantly easier.
  • 4.
    4 Parts List: Parts List ProductName Quantity Manufacturer Manufacturer Part Number Vendor Vendor Product Code PIC16F690 Microcontroller 1 Microchip PIC16F690 Microchip PIC16F690 PICKIT 3 Programmer 1 Microchip PG164130 Microchip PG164130 PIC Programming Socket – X55X Series 1 ARIES Electronics 28-6554-10 Digi-Key A302-ND Laptop w/ MATLAB & MPLABX Software 1 N/A N/A N/A N/A Voltage Source 1 Elenco XP-581A Elenco XP-581A Stepper Motor Controller 1 Texas Instruments DRV8825, md20b Pololu 2133 Stepper Motor 1 Pololu SY35ST28- 0504A Pololu 1208 FSR Force Sensor 1 Interlink Electronics 30-81794 Digi-Key 1027-1001-ND Lego Technic Set – Gears, Axles, Shafts 1 Lego N/A Lego Education N/A Switch 1 C & K Components JS202011SCQN Digi-Key 401-2002-1- ND 3-Axis Accelerometer 1 Pololu MMA7341LC Pololu 1247 Liquid Crystal Display 1 Lumex Opto/Components Inc. LCM- S01602DSR/B Digi-Key 67-1769-ND USB to TTL Serial Connection Cable 1 FTDI Chip TTL-232R-5V FTDI Chip TTL-232R-5V USB 2.0 to Mini- USB Cable 1 Qualtek 3021003-03 Digi-Key Q362-ND 5V Voltage Regulator 1 Texas Instruments 296-13996-5- ND Digi-Key 296-13996-5- ND Resistor, 3kΩ 1 Stackpole Electronics Inc. CF14JT3K00 Digi-Key CF14JT3K00TR- ND Capacitor, 220μF 1 Nichicon UVZ0J221MDD Mouser Electronics 647- UVZ0J221MDD Large Bread Board 1 PROAM 509-020 PROAM 509-020 Small Bread Board 1 PROAM 509-005 PROAM 509-005 Wire Kit 1 Elenco JW-350 Elenco JW-350 2-Pin Banana Cables 3 Pomona Electronics B-4-0 Digi-Key 501-1328-ND Long Pin-Out Strip 1 SparkFun 116 SparkFun 116
  • 5.
    5 Hardware Design: Our hardwaresetup is detailed in the following diagram: The hardware diagram shows the how all of the interactions between our circuit, microcontroller and mechanism work. Any arrows going out of a component represent outputs, and any arrows going into a component represent inputs. The clamping mechanism we designed is shown below:
  • 6.
    6 The mechanism shownhere was built using Lego gears, shafts and other various parts as a very rough prototype for the clamping mechanism that would be used on the Hyperloop pod build. This was more of a proof of concept than a mechanism that would actually be used. One key feature of this mechanism are the gears connected to the stepper motor that transfer the force from one shaft to another. The other key feature is the two clamping arms connected to adjoining gears through their shafts. Electronic Circuit Design: Our circuit used to test our first functionality is shown below: This circuit was used as a proof of concept more than anything. The LCD was used to display the decimal values recorded from the analog to digital conversion of the force sensor. Once we proved we could correctly measure the force values, we disassembled the circuit and moved to sending values to MATLAB through use of a COM port.
  • 7.
    7 Our final circuitfor the project is shown below: This circuit was used to take analog readings from a force sensor and send the digital equivalent to MATLAB. The other functionality of this circuit was to start and stop a stepper motor when the microcontroller determined it was a good time to do so. Our microcontroller was configured to take inputs from the switch and force sensor. The receive pin is connected to MATLAB through the use of a TTL adapter, as shown. It was also configured to output to the driver of the stepper motor and to the transmit pin connected to MATLAB. The driver of the stepper motor was connected to a 12V source with a 5V logic input from the microcontroller. The 12V power supply was connected to the ground through a 220μF capacitor for protection. Four of the pins provided output to the stepper motor and controlled its movements. The transmit and receive pins of the microcontroller were connected to a TTL adapter so they could be connected to a computer. Power and ground were also connected to this adapter so the computer would know a device was connected. All components that required 5V were supplied 5V through use of a voltage regulator. This provided protection in case a 5V power supply was not available.
  • 8.
    8 Programming: The microcontroller weselected was the PIC16F690. We selected this particular microcontroller due its ability to perform analog to digital conversion and its high number of pins for input and output. The pseudo code below outlines the general goals for our microcontroller ASSEMBLY program:
  • 9.
    9 Our detailed ASSEMBLYcode is shown below:
  • 10.
    10 The program utilizedfour major microcontrolling categories (analog to digital conversion (ADC), pseudo pulse width modulation (PWM), RS232 communication, and input/output). The input and output was primarily used to check whether or not the switch had failed and to take analog input from a force sensor (shown in the “Power” subroutine). The pseudo PWM was used to control the stepper motor. This was implemented by pulsing the step pin on the stepper motor driver at intervals determined by a delay loop. We decided to use this because it was easier to implement in the limited lab time so we could attempt to complete more of our functionalities (shown in “Step” subroutine). The RS232 was used to communicate with MATLAB and was implemented using the transmit and receive registers on the microcontroller (shown in SendW subroutine). The ADC was used to convert the voltage input from the force sensor to digital values that could be stored, analyzed and later transmitted to MATLAB for analysis (shown in the “ADC” subroutine).
  • 11.
    11 Our MATLAB codeis detailed in the diagram below:
  • 12.
    12 The MATLAB portionof the code follows the pattern of the diagram shown above. It takes inputs coming from the microcontroller and converts the digital values to voltages, and then to force values. The conversion from voltage to force was done by creating an equation through the use of regression. Known points were read from the Voltage vs. Force diagram (shown below) in the force sensor datasheet. These points were converted into log-log form for the curve fitting. When the fitting was complete, the equation was converted back to the non-linear form to be used by the main loop. The plot we used to perform our regression analysis is shown below: In the voltage divider circuit, a 3kΩ resistor was used for RM; this is because we desired the shallowest curve for more accuracy when using smaller force values. Testing/Proof of Operation/Conclusion: In reality, certain components of our project work very well, but we could not get them all to work in unison. For example, our live plot in MATLAB works extremely well as someone squeezes the force sensor with their fingers. The low-pass filter allows the force diagram to be almost entirely smooth with no noticeable noise. Also, as we run the MATLAB program, the stepper motor steps at a good rate and the lever arms clamp together. However, we could not get our clamping mechanism to produce a high enough force to be recognized by the sensor. This is because the mechanism wasn’t very robust; one of us had to fix the position of the mechanism and stepper motor to keep them from rotating with the lever arms. Another thing that contributed to this was that the surface between the two lever arms did not provide a good enough clamping surface to be recognized by the force sensor. The only other remaining bugs from our main goals are the switch not working and the motor not stopping when the selected force value is applied. In the current state of the project, when the circuit is plugged into a 5V and 12V supply, there should be no moving components, but the stepper motor should hum. When the MATLAB program is run, the stepper motor should start rotating at a consistent speed, and a plot should appear on the screen of the computer. If the force sensor is squeezed, the live updating plot should show an accurate representation of how the sensor was squeezed.
  • 13.
    13 An example ofone of our Force vs. Time plots is shown below: Potential Improvements/Future Work: Although we were able to accomplish a lot over a short time period, there is a lot more work to be done with our project. Some of the things we would like to accomplish in the future are:  We would like to compare the results from our stepper motor mechanism to the results we would get from a solenoid to see which provides a more consistent clamping force on the sensor. The reason we weren’t able to complete this is that the time constraints did not allow for enough time to to research and order a proper solenoid for the project.  It would be great to build a more robust clamping mechanism to minimize fluctuations and inaccuracies in the force data. We had trouble with the fact that our mechanism wasn’t
  • 14.
    14 squeezing the forcesensor as tightly as we wanted, so we think a better design could remedy some of our major issues.  We need to simulate an electrical failure using a switch. We were close to getting this functionality working before the project deadline, so we would just need to debug our code further to achieve this.  Eventually, our ultimate goal is to clamp to an optimal force value based on the pod’s acceleration, which we want to mimic with an accelerometer. This would allow our pod design to reach a controlled and comfortable stop.  We would like to research clamping materials to get an optimal coefficient of friction for use on a Hyperloop pod.  After all our functionalities are complete, we would like to test our idea using a small-scale version of our Hyperloop pod design. Troubleshooting: One difficulty that we had with the project was trying to get the stepper motor to stop stepping after reaching a certain force value. It seemed like we had the logic correct, but a minor error in the code or wiring may have caused it to malfunction. Another issue we had was using the switch to trigger the response of the stepper motor. For some reason, we couldn’t get the port to recognize when the switch was flipped. When troubleshooting earlier parts of the project, commenting out specific sections or lines of code were useful for evaluating which parts of the code were actually working. Also, when applicable, it really helped us to use the debugging tool in MPLABX. What We Have Learned: This project was our first exposure to controls and the first place that we could apply our knowledge of circuits in a practical way. What we would like to take away from this project and apply to our careers is the ability to take a very complex project, and break it into many simple functionalities. By utilizing the information taught to us during lecture and looking through data sheets for our requested components, we were able to work our way through numerous challenges presented by our choice of project. Theoretical topics such as 8-bit and 10-bit mathematics were vital for our functionalities, so learning that material during lecture really aided us in practice.
  • 15.
    15 Appendices: ASSEMBLY Code –Team2_Final_Project.asm: ;Authors: Jacob Grendahl, Tristan Roberts ;Date: May 6, 2016 ;Class: AME 487 ;Assignment: Final Project ;File: Team2_Final_Project.asm ; ;Description: ; This is meant to program a PIC16F690 ; The controller is supposed to control an emergency braking system ; through use of analog input from a force sensor, and output to a stepper motor. ; When matlab begins to listen and power failure has been simulated, the stepper ; motor should begin to step. ; ; When the optimal force value is reached, the stepper motor should stop stepping. ; The controller should be sending the digital force values to matlab indefinitely. List P=16f690 #include <p16f690.inc> ;Codeprotect on, watchdog off, internal high speed osc, powerup timer on, clear reset off, brown out off __CONFIG _CP_ON & _WDT_OFF & _INTOSCIO & _PWRTE_ON & _MCLRE_OFF & _BOR_OFF CBLOCK 0x20 temp num Dlay Period OutputVal Check CheckH ENDC org 0x00 goto start ;***************************************************; ;Initialize Oscillator, 8MHz internal ;***************************************************; start ; ADC & MATLAB Setup bsf STATUS, RP0 ; switch to Bank 1 MOVLW b'01110000' ; Set internal oscillator frequency to 8 MHz MOVWF OSCCON
  • 16.
    16 bcf STATUS, RP0; Switch to Bank 0 clrf PORTC clrf PORTB clrf PORTA bsf STATUS,RP1 ; bank 2 BSF STATUS,RP0 ; Bank 1 clrf TRISC bsf TRISB,RB5 ;set RB5 as input to RX from RS232 BCF STATUS,RP0 ; Bank 0 BCF STATUS,RP1 ; BANKSEL ADCON0 movlw b'10000001' ;Right justify and start ADC unit MOVWF ADCON0 BSF STATUS,RP0 ; Bank 1 movlw b'00110000' MOVWF ADCON1 ;configure ADC unit bsf STATUS, RP1 ; Bank 3 BSF TRISA,0 ; Set RA0 to input BSF TRISA,1 ; Set RA1 to input BCF TRISB,4 ; set RB4 as output BCF TRISB,6 ; set RB6 as output BCF STATUS,RP0 ; Bank 2 BSF ANSEL,0 ; Set RA0 to analog BCF ANSEL,1 ; Set RA1 to digital BCF ANSELH,2 ; set RB4 as digital BCF ANSELH,3 ; set RB5 as digital BCF STATUS, RP1 ; bank 0 ; Stepper Motor Setup movlw 1 << 2 ; Start with Bit 2 Active movwf PORTC movlw 7 ; Turn off Comparators movwf CM1CON0 movlw b'00000011' ; RC5:RC2 are Outputs banksel TRISC movwf TRISC bcf STATUS, RP0 ; Return Execution to Bank 0 movlw 1 << 2 ; Initialize the Output Bit movwf OutputVal
  • 17.
    17 call SetUpRS232 ; thefollowing segment waits for a external command (128) recd by RS232 ; then sends back the value of the ADC storred in Speed ; RB5 is RX for RS232 and also external interrupt on port change ; RB7 TX transmit ;call Init_SPI ;Set RA0 for analog input BCF STATUS,RP1 BCF STATUS,RP0 ; Bank 0 BANKSEL ADCON0 movlw b'10000001' MOVWF ADCON0 BSF STATUS,RP0 ; Bank 1 movlw b'00110000' MOVWF ADCON1 bsf STATUS, RP1 ; Bank 3 BSF TRISA,0 ; Set RA0 to input BCF STATUS,RP0 ; Bank 2 BSF ANSEL,0 ; Set RA0 to analog ;***************************************************; ; Check 128 ; ;***************************************************; Check128 ; enable receiver banksel RCSTA bsf RCSTA, CREN ; wait until a byte has been received btfss PIR1,RCIF goto $-1 movf RCREG,w ; send name if rcvd char is 128 sublw .128 btfsc STATUS,Z goto Power goto Check128 ;***************************************************; ; Set up RS232 ; ;***************************************************;
  • 18.
    18 SetUpRS232 ;Initialize the transmitter BANKSELTXSTA ;Goto Bank 1 BCF TXSTA, SYNC ;Asynch mode BSF TXSTA, TXEN BSF TXSTA, BRGH ;19.2k 8MHz BCF BAUDCTL, BRG16 ;19.2k 8MHz ; BSF TXSTA,TX9 ;enable 9-bit transmission (stop bit) ; BCF TXSTA,TX9D ;stop bit is set to 1 MOVLW 0x19 ;19.2k 8MHz MOVWF SPBRG ;19.2k 8MHz BANKSEL RCSTA ;Bank 0 BSF RCSTA, SPEN ;Enable serial port RETURN ;***************************************************; ; Power Failure ; ;***************************************************; Power ; btfss PORTA,1 ; is power still on? ; goto Power ; Yes movlw b'00000000' ;Initialize Check movwf Check goto Loop ; NO ;***************************************************; ; Loop ; ;***************************************************; Loop call ADC ;Gather force data call check btfss Check,0 ;Continue Stepping? call Step ;Yes movfw ADRESH andlw b'00000011' ;ensure data is clean (no bad data) call SendW ;send high force movfw ADRESL call SendW ;send low force goto Loop ;***************************************************; ; Analog to Digital Conversion ;
  • 19.
    19 ;***************************************************; ADC movlw 5 ;Wait some usecs for ADC to Charge addlw 0x0FF ; Take One Away to Setup the Charge btfss STATUS,Z ; Check the zero bit goto $-2 bcf STATUS, RP0 bcf STATUS, RP1 ; Bank 0 BSF ADCON0,GO ; Start conversion BTFSC ADCON0,GO ; Is conversion done? GOTO $-1 ; No, test again return ;***************************************************; ; Check ; ;***************************************************; check btfss Check,0 ;checks for already being stopped goto run BANKSEL PORTC clrf PORTC BANKSEL TRISC bsf TRISC,2 BANKSEL PORTC return run bcf STATUS,C ;movlw b'00000010' ;High bits for binary 517 ;movwf CheckH movlw b'11110001' ;low bits for binary 517 addwf ADRESL,w ;start of 10 bit addition btfsc STATUS,C bsf Check,0 ;incf CheckH ;if low bit overflow increment ;movfw ADRESH ;andlw b'00000011' ;addwf CheckH,f ;check high order bits ;btfsc CheckH,2 ; incf Check ;if high order "overflow" set check return
  • 20.
    20 ;***************************************************; ; Step ; ;***************************************************; Step BANKSELPORTC movlw d'230' movwf Period movlw 0x80 ; Forwards or Reverse? subwf Period, w Forwards: ; Move Stepper Forwards xorlw 0x7F ; Negate the Value for Delay movwf Period rlf OutputVal, w ; Shift the Saved Value andlw b'00111100' btfsc PORTC, 5 ; Roll Over? iorlw 1 << 2 movwf PORTC movwf OutputVal ; Save New Set Bit DlayLoop: ; Repeat Delay Loop for "Period" movlw HIGH ((1000 / 5) + 256) movwf Dlay movlw d'25' addlw -1 btfsc STATUS, Z decfsz Dlay, f goto $ - 3 decfsz Period, f goto DlayLoop return ;***************************************************; ; Send Work Register ; ;***************************************************; SendW ;check status of transmit bit, wait until set BANKSEL TXSTA BTFSS TXSTA, TRMT GOTO $-1 BANKSEL PIR1 BTFSS PIR1, TXIF GOTO $-1
  • 21.
    21 BANKSEL TXSTA BSF TXSTA,TX9D;stop bit is set to 1 ;Load working register into TXREG BANKSEL TXREG MOVWF TXREG ;Wait until character is sent BANKSEL TXSTA BTFSS TXSTA, TRMT GOTO $-1 skipsend RETURN END
  • 22.
    22 MATLAB Code –ForceConversion.m: %Names: Jacob Grendahl, Tristan Roberts %Date: May 6, 2016 %Class: AME 487 %Assignment: Final Project %File: ForceConversion.m % %Description: % This file is responsible for converting the binary bits recieved % into force values. This is achieved by first creating an equation % that converts voltage to force, then running through the main loop. % The main loop constantly times the conversions and updates a force vs % time plot. out=instrfind(); delete(out); clc;clear; run('Regression'); s = serial('COM6'); %Serial port configuration set(s,'BaudRate',19200); set(s,'InputBufferSize',2); %-------------------------------------------------------------------------- fopen(s) %Open serial port N = 500; fwrite(s,128,'async') %Send interupt signal to the microcontroller ii=2; t(1)=0; while ii<=N tic out(ii,1) = fread(s,1,'uint8'); %Read data from the input buffer switch out(ii,1) case 3 out(ii,1)=2^9+2^8; case 2 out(ii,1)=2^9; case 1 out(ii,1)=2^8; case 0 out(ii,1)=0; otherwise out=out(1:ii-1,:); continue end out(ii,2) = fread(s,1,'uint8'); %Read data from the input buffer b=toc; t(ii)=t(ii-1)+b; Vout(ii)=(out(ii,1)+out(ii,2))/1024*5; %DAC for voltage readout F(ii)=Func(Vout(ii)); F(ii)=lowpassfilter(F(ii-1),F(ii)); plot(t(1:ii),F(1:ii),'--k');
  • 23.
    23 drawnow xlabel('Time (s)'); ylabel('Force (N)'); title('Forcevs. Time'); ii=ii+1; end %-------------------------------------------------------------------------- fclose(s) %Close serial port delete(s) clear s
  • 24.
    24 MATLAB Code –lowpassfilter.m: %Names: Jacob Grendahl, Tristan Roberts %Date: May 6, 2016 %Class: AME 487 %Assignment: Final Project %File: lowpassfilter.m % %Description: % This file removes noise from the force values that are taken function F=lowpassfilter(F0,F1) F=0.5*F0+0.5*F1; end
  • 25.
    25 MATLAB Code –Regression.m: %Names: Jacob Grendahl, Tristan Roberts %Date: May 6, 2016 %Class: AME 487 %Assignment: Final Project %File: Regression.m % %Description: % This file is resopisible for building the equation that converts % voltage to force values. F=9.8/1000*[20 50 95 195 310 440 570 705 900 1000]; V=[0.35 0.5 0.7 1 1.2 1.45 1.625 1.8 1.95 2]; X=log(V); Y=log(F); Z=[ones(length(V),1) X']; A=Z'*Z; b=Z'*Y'; a=Ab; x=0:0.1:5; y=exp(a(1)).*x.^a(2); Func=@(x)exp(a(1)).*x.^a(2); plot(V,F,'or',x,y,'-k'); xlabel('Voltage Out (V)'); ylabel('Force (N)'); title('Force vs. Voltage Output');
  • 26.
    26 The necessary datasheets required to complete this project are attached in a separate folder labeled “Appendices.” The included data sheets are as follows:  PIC16F690, Microchip  FSR Force Sensor, Interlink Electronics  SY35ST28-0504A Stepper Motor, Pololu  DRV8825 Stepper Motor Controller, Texas Instruments A lot of the information we used about the stepper motor and stepper motor controller came from the following links:  Stepper Motor: https://www.pololu.com/product/1208/resources  Stepper Motor Controller: https://www.pololu.com/product/2133
  • 27.
    27 Works Cited DRV8825 StepperMotor Driver Carrier, High Current. Tech. Pololu, n.d. Web. 28 Apr. 2016. FSR Integration Guide. Tech. Interlink Electronics, n.d. PDF. 28 Apr. 2016. Hyperloop Alpha. Tech. SpaceX, 12 Aug. 2013. PDF. 28 Apr. 2016. Hyperloop Braking System Render. Digital image. Delft Hyperloop. Mkb Brandstof, 22 Jan. 2016. Web. 28 Apr. 2016. PIC16F690 Data Sheet. Tech. Microchip, n.d. PDF. 28 Apr. 2016. SY35ST28-0504A Stepper Motor Data Sheet. Tech. Pololu, n.d. PDF. 28 Apr. 2016. The University of Arizona Air Bearings & Suspension Hyperloop Pod Subsystem Design. Tech. Tucson: The University of Arizona Hyperloop Competition Team, 28 Jan. 2016. PPT. 28 Apr. 2016.