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PowerBot Group #2: Tarik Ait El Fkih Luke Cremerius Marcel Michael Jerald Slatko Sponsored By: Aeronix, Inc. Project Description Autonomous robot purposed to provide supplemental power to mobile devices (laptops, mobile phones, etc.). Uses onboard navigation algorithms to navigate to user’s location. Incorporates an iOS application to provide robot statistics and manual control. Project Motivation Battery life longevity in mobile devices is a constant issue. Wanted to create a charging solution that could charge the device without inconveniencing the user. The device would be simple to use, allowing for easy adoption into a users everyday routine. Objectives PowerBot should be able to navigate autonomously to a user’s location. PowerBot should be able to be remotely controlled by the user through the use of an onboard camera and the provided iOS application. PowerBot will contain a battery used to charge external devices through the use of inductive and USB interfaces. Specifications Will be at most 36” long Max speed of 5 mph Battery life of minimum 24 hours Ability to provide charge to mobile devices 100% of the time. Switching Voltage Regulators Needed to regulate power to the different systems in PowerBot. Highly efficient when compared to linear voltage regulators; 1440% vs. 85-90%. Inductive Charging 9 V switching regulator: LT1424-9 Used to step down voltage for charging mat. SO-8 package. Charging mat offers a degree of flexibility due to lack of wires. Inductive cases are needed unless implemented (Qi) by manufacturer. USB Charging 5 V switching regulator: DESW050 Used to step down voltage for USB charging. Pin-compatible with 78XX family (TO-220 package) of linear voltage regulators. USB, although wired, is, well, universal. Microcontroller Supply 3 V switching regulator: DESW033 Used to step down voltage for the microcontrollers. Pin-compatible with 78XX family (TO-220 package) of linear voltage regulators. Motors Stepper Motor: To be used to rotate (Θ-axis) the solar panel. Brushed DC Motor: To be used to drive the rear wheels. Motor Specifications Part Number SST58D3830 RS-540 Manufacturer Shinano Kenshi Tamiya Stepper DC Brushed Step Angle (°) 1.8 N/A No Load RPM N/A 16,800 Voltage (V) 2.1 4.5-12 Current (A/Phase) 3.0 1 (no load) Resistance (Ω/Phase) 0.7 N/A Inductance (mH/Phase) 1.3 N/A Holding/Stall Torque (kg-cm) 7.3 2.84 Rotor Inertia (g-cm3) 290 N/A Weight (kg) 0.71 0.153 54 mm 50 mm Type Dimension (L) Motor Controllers MSP430F123 will be used to control the solar panel [stepper] motor. Contains hardware UART for serial communications. Motor Controllers MSP430F2616 will be used to control the DC brushed motor. Its features: Interfaces with UART. 16 MHz with 4 kB of RAM and 92 kB of flash memory. 48 GPIOs. ADC resolution of 12 bits with 8 channels. R/C Car Chassis Somewhat standard overthe-counter licensed R/C car. Large wheels allow for maneuverability. Chassis Modifications Swap out the drive motor to (DC Brushed). Remove the [red] plastic body frame and create a foundation for PowerBot. Obstacle Avoidance Obstacles will be detected using ultrasonic ranging sensors As PowerBot moves, the ultrasonic sensors rapidly take readings to gather range data in real time. The obstacle avoidance algorithm will maneuver PowerBot in response to the presence of obstacles. Three modes of operation: Active Adjustment (AA) Reverse-Reset (RR) Off Obstacle avoidance is OFF by default. It must be enabled by the iPhone user Modes of Operation Active Adjustment (AA) Primary mode of operation Front two ultrasonic sensors are active A range reading within the AA minimum distance causes PowerBot to steer either left or right to avoid it. PowerBot will attempt to re-align Ultrasonic Sensors LV-MaxSonar® – EZ0™ Operates at 2.5 V – 5.5 V Avg. current draw: 2 mA Min. Distance: 6 in. Obstacles closer than 6 in. give reading of 6 in. Max. Distance: 254 in. (21 ft.) 1 inch Resolution Range readings can be taken at about 20 Hz, every 50 ms. Output modes include: Analog Pulse Width UART (not quite RS-232) Image Credit: www.maxbotix.com PIC32 Microcontroller PIC32 family of microcontrollers was chosen to drive PowerBots navigation and Wi-Fi communication functions. The PIC32 features an 80 MHz clock with onboard 512 kB of flash and 128 kB of RAM. Model Number: PIC32MX695F512H Wi-Fi Communication • Used as the primary mode of communication between PowerBot and the iOS application. • 802.11 Wi-Fi used as a physical layer with TCP sockets used for higher level communication. Embedded Software iOS Software Application Layer Application Layer MCU – Serial iOS – Serial 802.11 – Socket 802.11 – Socket Wi-Fi Module: MRF24WB0MA • The MRF24WB0MA microchip provides a complete Wi-Fi solution for onboard communication with PowerBot. • The Microchip TCP/IP stack works with the MRF24WB0MA and allows for easier implementation of sockets and the passing of data via TCP. PIC32 Wi-Fi Circuit Board Microchip Wi-Fi Comm Development Board was used for prototyping. Custom circuit board was based off of this design. Combines PIC32 MCU with the MRF24WB0MA Wi-Fi module. Additionally gives access to 4 UART ports, as well as 6 GPIO pins used for ultrasonic sensor data acquisition and motor commands PIC32 Wi-Fi Circuit Board PTR 1 PA D1- 13 PTR1 PA D1- 13 PTR1 PAD 1- 13 .1uF C4 TP4 PTR1 PAD 1- 13 TP5 SV4 TP3 .1uF C5 8 LED1 TP1 S1 R8 10K 470 R7 SV3 1 LED2 PIC32MX695F512H 8 C6 .1uf 8 2 SV2 1 R6 4.7K 100K R5 1 LED3 .1uF 10uF C2 C1 1 X1 C3 .1uF 10K R9 SV1 6 R1 R2 1K R3 1K 1K 100K R4 .1uF C8 10uF C7 1 11/11/2012 4:55:28 PM f=3.00 C:\Users\Luke Cremerius\Desktop\Senior Design Wifi Board Eagle Files\wireless board mods.b PIC32 Wi-Fi Board Layout Software Layout iOS Application PowerBot Obstacle Avoidance Algorithm Motor Control Power Management Sonar Sensors Stepper Motor Solar Panel Charging Ports iOS Application Written in Objective-C using Xcode 4.4. Provides users access to: Manual mode Obstacle Avoidance Ultrasonic sensor status Manual Control Gives the user manual controls to drive PowerBot. Sensor icons blink when currently taking distance readings. Status of Wi-Fi connection shown above robot controls. System Status Shows the user the current sensor status of PowerBot. Displays the onboard sensor distance readings Shows the number of readings received from each sensor I/O Data button allows viewing all incoming TCP data System Settings Allows the user to open a socket connection to PowerBot once the user has joined the ad-hoc network PowerBot broadcasts. Toggle button for turning obstacle avoidance on or off. Power Battery Requirements 24 V battery At least 2 Ah Deep cycle for increased usage time Low internal resistance Flat discharge rate Lightweight Battery Choice SPECIFICATIONS Ni-Cd Ni-MH Li-ion Li-Po Energy Density (W·hr/kg) 40–60 70-90 100-160 130-200 Capacity (Amp-hr) 1 2.4 2.8 2.6 Internal Resistance (mΩ) 100-200 200-300 100-200 200-300 Nominal Voltage (V) 1.2 1.2 3.6 3.7 Discharge Rate Flat Flat Flat Flat Recharge Life 500-700 cycles 600-1000 >600 >1000 Disposal Must be recycled Recyclable Recyclable Recyclable Charge/Discharge Efficiency 70-90 % 66 % 80-90 % 99.80 % Cost ($/Whr) 2 2.75 2.5 2.8-5 Lithium Polymer Battery Polymer Li-Ion Battery 18650 cell type 14.8 V (working) 16.8 V (peak) 2.2 Ah 32.56 Wh Reasons for choosing: • High energy density (Wh/kg) • High energy/dollar (Wh/$) Alternative Power Source Power outlet: “Unlimited” power Quick charging of the battery Solar panel: Environmental Impact Financial Benefits Energy Independence Solar Panels Specifications Monocrystalline Polycrystalline Thin film Power 10 W 10 W 10 W Open Circuit voltage 21.5 21.4 24.2 Short Circuit Current 0.64 0.68 0.84 Maximum Power Voltage 17.5 16.8 17.3 Maximum Power Current 0.57 0.6 0.64 Efficiency 15 % 12.5 % 6.3 % Cost/W 10-11 8.5-9.5 10 Solar Power Selection Details Solar Panel Type Monocrystalline Manufacturer INSTAPARK Efficiency 15 % Power 10 W Maximum Voltage Power 17.5 Maximum Current Power 0.57 A Open Circuit Voltage 21.95 V Cost $39.95 Output Efficiency Increasing the output efficiency of the panel: Increase panel size Implement tracking system Single axis Dual axis Single Axis Control System Ambient Light Photoresistor MSP430 Longitude Orientation Dual Axis Control System Latitude Orientation Ambient Light Photoresistor MSP430 Longitude Orientation Compare and Contrast Dual axis control system would require more maintenance. There’s an extra cost involved in utilizing an extra motor or actuator. Increased complexity. 6% extra efficiency compared to a single axis control system; not worth it. Solar Panel Implementation Free rotation of theta (𝜃) angle. Phi (𝛷) is fixed in single axis system. Optimal angle of phi (𝛷) is 15°. Budget Part Cost Quantity Total Cost RC Car Chassis $50 1 $50 Solar Panel $40 1 $40 Inductive Charger $40 1 $40 Battery $105 2 $210 Dev Board $50 1 $50 PICKit 3 $50 1 $50 Sonar Sensors $30 10 $300 Motors Circuit Components Total ~$550 Distribution of Labor Tarik Luke Marcel Jerald Solar Panel 80% 5% 10% 5% MCU Software 25% 25% 25% 25% Robot Construction 10% 5% 80% 5% Wireless Design 5% 70% 5% 20% Navigation/AI 5% 20% 5% 70% Concerns Ability to accurately depict a global map and link it to PowerBot’s local map. Ability to correctly implement EERUF. Ability for PowerBot to become unstuck in a trap situation. Questions?