RoboTeam 05/04/2012 Submitted by:Costia Parfeniev, Boris Pinzur Supervised by: Kobi Kohai

Agenda Project Goals Design Zigbee™ Explained Architecture Modules Breakdown Encountered Difficulties Suggestions for improvements

Project goals Develop a wireless communication infrastructure among several robots for future projects. The project shall provide a simple software API for future reuse. The design shall allow using more than 2 robots by revising the application. Create an autonomous system of two robots. Demonstrate the ability to coordinate movement and activity using the Zigbee™ wireless comm.

Design Using a standard 2 level robot base. Which includes: Chassis 2 Servo motors Wheel encoders MSP430 as the main application processor. EZ430-RF2480 board as the communication module. A rotating sensors turret with: 2 IR distance sensors. IR LED Array beacon. IR photodiode.

Zigbee ™ Explained The Zigbee protocol is a low-power, low-resource devices, with an easy to use API. Supports several network topologies Zigbee network consists of a coordinator and several routers or end devices Black: Coordinator Red: Router White: End Device

Zigbee ™ HW PC Interface: End Device

Power Data Physical structure Zigbee board EZ430-RF2480 CC2480 MSP 430F2274 MSP430 Board MSP-TS430PZ100 MSP430 Board MSP-TS430PZ100 MSP430FG4618 Mobility Left Servo Right Servo Right Encoder Left Encoder Sensors Turret Servo Forward IR Distance Sensor Back-Facing IR Distance Sensor Close range Discovery IR Beacon Forward IR Photodiode Upper Power Supply (5V,3.3V) Lower Power Supply (5V)

Robot Images

Software/Logical structure Application Remote Communication module Local Wireless Network Sensors Motors Close-range communication and discovery

The module is based on the EZ430-RF2480 board, controlled the main MSP430FG4618 µC Remote Communication: EZ430-RF2480 CC2480 MSP430 F2274 MSP430 Board MSP-TS430PZ100 MSP430 Board MSP-TS430PZ100 MSP430 FG4618 RF Antenna SPI UART

Close range discovery system IR receiver IR Beacon Purpose: Identifying near-by robots. Hardware: Beacon array - IR LED IR photodiode IR Distance sensor Servo IR Range Sensor

Motors Purpose: Mobility and control infrastructure. Hardware: 2 servo motors 2 encoders

Application The application works in several stages: Initialization and calibration Turn on all HW modules and calibrate the servos. Discovery Use of IR sensor, beacon and distance sensor to find adjacent robots (Zigbee is used to announce any discovery to the network). Alignment Use IR distance sensors to get the robots closer and align them. Movement The robots use IR distance sensor to periodically correct distance and alignment errors, and transmit the sensor’s results to each other.

Encountered Difficulties Received IR signal shape is dependent at varying distances. Received data from the IR requires error detection. Calibration – different timings, speed and angles for the servos. Some of the parts are of different models on each robot. Timing jitter due to ADC sampling and long interrupt handlers. Zigbee operation and integration. IR LED narrow angle. Not enough timers on the chip.

Suggestions for improvements OS like infrastructure – reduce real-time tasks using threads. Generalized local coordinate system (turret, body, encoder wheel). Fully autonomous calibration. Power consumption analysis and reduction. Data transmission over IR. Simulator for application testing before trying it on HW. Complex distributed applications.

Movement Coordination Demo Video

Thank you !