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Navigation System for an RC Helicopter

Boeing’s long-term objective is to build a remote controlled (RC) helicopter that can fly autonomously.  The helicopter will then be used to develop sophisticated control systems.  The first step to complete this project is to equip the helicopter with a navigation system which includes a Global Positioning System (GPS) and an Inertial Measurement Unit (IMU).  These two sensors will have the ability to accurately measure 3-dimensional position, velocity, acceleration, and angular motion in real time. The next step will be to transmit the data to a ground station that will be used for flight testing and control system development. Boeing is looking for a team to implement the first stage of design and encourages an investigation into the second stage.  We are required to keep the weight of all electronics and mounting equipment under five pounds, and to transmit data from the helicopter to the ground station a minimum distance of 300 meters.

Members of our team have recently worked on a similar GPS system that transmits data. We are familiar with interfacing a GPS receiver to a microprocessor, creating board layouts, and have a good understanding of telemetry systems. By applying this knowledge, we will complete both the first and second stages of this project.

Solution Procedure:

Our solution will satisfy Boeing’s immediate requirements and will be expandable in future development efforts.  We are also emphasizing the use of “single-chip”/”off-the-shelf” units to reduce design complexity and development cost.  Our physical solution will implement the following procedure:

1.      Data packets from the GPS and IMU will be processed by the microcontroller.

2.      The microcontroller will route these data packets to the helicopter transceiver.

3.      The ground station will receive this data and send it to a laptop via serial port.

4.       Software on the laptop will display the GPS and IMU data and store it to a file. 

Block Diagram:

Component Information:

We have chosen to use a Triscend E520 40MHz microcontroller unit.  This microcontroller is a combination of an Intel 8052 microprocessor and an FPGA.  The FPGA has over 2000 programmable logic cells which can be used in place of circuit board components. These logic cells can be reprogrammed to change and/or add functionality. This ability will eliminate the need to redesign the circuit board, thus making future development easier.  We will simulate two RS-232 ports in the FPGA to connect the Intel 8052 to the IMU and GPS unit.   

The GPS unit will be a commercial grade receiver from CMC Electronics called the Superstar II.  We chose to use a commercial receiver for several reasons.  First, they are smaller and cheaper than military grade receivers.  Second, though they are less accurate, improvements such as position averaging and the use of a reference base station can be used to increase accuracy.  The GPS unit will provide the helicopter's latitude, longitude, and height above the ground, as well as its 3-dimensional velocity.

A Crossbow IMU400CC-100 has been provided by our advisor.  The IMU will provide the helicopter's pitch, yawl, and roll rates, as well as its 3-dimensional acceleration. 

We chose the Honeywell HRF-ROC09325XM Transceiver as our telemetry link.  We chose this transceiver because it came in an evaluation board which would greatly ease its integration.  We will simulate an RS-232 port in the FPGA to connect the microprocessor to the transceiver.  The microcontroller will input data from the GPS unit and the IMU and forward it to the ground via the transceiver. 

The electronics will be powered by one 9.6V rechargeable battery, independent of the helicopter power system.  To power the electronics for a longer period of time between recharging, a second battery will be used just for the IMU.  This change can be made without making any modifications to the power system.

All electronics on board the helicopter will be mounted to withstand vibration caused by the helicopter.  Excessive vibration would cause component damage and add error to the IMU sensor measurements.  We will use RTV to protect the circuit board components, and we will encase all of our electronics in foam.  

The base station will be a standard IBM laptop with software that will read data from a transceiver tuned to the helicopter’s transceiver frequency.  Our team will write software that will display the GPS and IMU data and store it to a file.

Team Members: Jason Acierno, Mark Fallet, Randy Grossman, Brendan Surrusco

Team Advisor: Joe Horn - 233 Hammond Building, University Park, PA

Boeing Contact: Patricia Stevens - Ridley Park, PA