Android controlled robot
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This document describes an Android-controlled robot project. An Android application allows a user to remotely control a robot vehicle via Bluetooth. The application sends throttle and steering commands to a microcontroller via a Bluetooth modem. The microcontroller controls DC motors through a motor driver to drive the robot. Sensors, advanced motion control, obstacle avoidance, and vision-based capabilities are proposed for future extensions. The project was a learning experience in mobile app development, electronics integration, and bringing a design from concept to implementation.
Android controlled robot
- 1. Android-Controlled Robot Ben Johnke ECE561 Final Project December 16, 2013 1
- 2. Project Overview • What? – Vehicle which can be controlled remotely by an Android smartphone • How? – Write an Android app which allows the user to provide throttle and steering inputs – The app sends commands via Bluetooth – Commands received by Bluetooth modem connected to microcontroller – Microcontroller controls motors 2
- 5. Drivetrain • Vehicle driven by left and right DC motors • Motor torque spec based on estimated vehicle weight, desired acceleration • Differential steering employed – Turn vehicle by driving motors at different velocities – Ball casters in front allow pivoting; no additional wheels needed 5
- 7. Power Source • Few battery technologies can provide high current • Max. discharge rate specified by “C”-rating – C = battery capacity in amp hrs. – NiMH: ~1C – LiPo: 10C+ • LiPo selected to meet this application’s high-current needs – 6A stall current per motor – Chosen battery has 4.0Ah capacity and 25C discharge rating 7
- 9. Motor Driver • Motor control requires full processor attention – Monitor motor speed – Continuously adjust motor voltage to minimize error between desired and actual motor speeds – Essentially a digital feedback control system • Want to avoid this additional hardware and software complexity • Solution: Pololu Dual Motor Driver Shield for Arduino – Contains 2 STMicroelectronics VNH5019 motor drivers, each rated for 12A – Includes Arduino library allowing motor speeds to be set with simple function call 9
- 11. Microcontroller • Arduino UNO – 14 digital I/O pins which can also be used for serial communication – On-board regulated 5V supply – Works with Pololu Motor Driver Shield • Implements differential steering algorithm – Outside wheel speed set based on throttle command alone – Inside wheel speed also set based on throttle command, but subtracted from according to sharpness of steering angle – Rate limiter keeps speeds from changing too quickly 11
- 13. Bluetooth Modem • Want Class 1 Bluetooth for long range (~100m) – Chosen model: BlueSMiRF Gold • Essentially implements a wireless serial stream – When modem receives a message via Bluetooth, it sends that message via serial – When modem receives a message via serial, it sends that message via Bluetooth • Has static network address which Android controller uses to establish a connection 13
- 15. Android Controller Application • Creates socket for communicating with Bluetooth modem, using its known address • Reads throttle and steering slider bar values, transmits periodically on socket’s OutputStream • Listens on socket’s InputStream for error messages from Arduino 15
- 16. Lessons Learned • Skills – – – – Android app development (Java, XML) Selecting parts based on datasheets Practical aspects: sourcing parts, mechanical fabrication Bringing a design from concept to implementation • Conclusion – It is feasible to implement Bluetooth communication between smartphone and microcontroller – This opens door for wide range of possible similar applications • Remote starter for car • Automation of household tasks 16
- 17. Future Extensions • Advanced motion – i.e. robot arm controlled by servo motor • Obstacle avoidance – Install proximity sensor; develop algorithms to steer around / back up when obstacles detected • Vision – Use camera to transmit frames back to Android application for display to user – Bluetooth too low-bandwidth; switch to WiFi 17
Editor's Notes
- #4: -Power source for microcontroller and motor driver-Microcontroller receives commands from smartphone via Bluetooth modem-Microcontroller then sends appropriate signals to motor driver
- #12: -Serial communication via computer, BT modem-5V supply to power BT modem
- #14: Arduino interacts with modem just as it would any other serial connectionSits on static network address and listens for any attempted connections