Tractor Auto Steering Calibration Device

Embedded Systems
Description
Automated calibration/characterization system for use in agricultural based automatic steering guidance applications. Device supports customizable routines for automated electronic steering control of agriculture machines and collection of machine sensor data, on-board inertial data, and positional/attitude information from external GPS unit. Collected data/results stored on removable SD card.
Project Overview
My group and I designed a device that can easily connect to any machine in addition to a positional system with simple adapter cables to be used to automate the calibration process to find the steering profiles of these machines. The intention was to provide a simple interface that will walk the operator through the process of conducting tests that will automatically be completed by the device, where it will also collect live information about the state of the machine from the positional system and additional sensors on the device and from the machine. The recorded information from all tests can be used to produce a more accurate steering profile of the machine which can be used to improve steering performance of self-driving tractors.

mbed framework

mbed LPC1768

IMU

GPS

Analog Chips

CAN Bus

SD Card

The microcontroller  used is the MBED LPC1768 Evaluation Board. We chose this board because it is a development-friendly board and it has sufficient functionality to support all of our design criteria. A high-level overview of our design requirements are as follows -

  • 2 CAN Bus communication lines
  • SPI pins for our SD card, IMU and LCD screen
  • PWM capabilities
  • Serial pin for output data from the GPS

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GPS Positioning Information

Our device can collect positional data from an external GPS unit mounted on the machine. The GPS unit outputs a RS-232 based communication signal that will contain the current position along with additional information about the accuracy and quality of the data.

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CAN Bus Interface

The CAN system is made up of two different CAN buses, one for the steering control and one for the miscellaneous information on the machine. For the steering CAN system, our board's CAN pins are connected to the steering bus of the machines that support steering over CAN and is responsible for the steering commands of the machine.

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Analog Voltage Interface

For older machines that do not support steering commands over the CAN bus interface, our project achieves steering control by supplying voltage to the machine’s valves.

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SD Card Storage

The SD card is used to store the data collected which can then be analyzed during the testing process. Each test will involve collecting positional data from the GPS and attitude information from the IMU, which is stored on the SD card along with additional diagnostic information.

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Internal Measuring Unit (IMU)

An IMU is a device that consists of gyroscopes and accelerometers to measure the angular rate and acceleration of the object to which it is attached. We chose to use the OpenIMU300 which contains its own processor to offload the reading and processing of the sensors from the main microcontroller. The IMU is used to calculate roll, pitch, and yaw information of the machine in addition to the raw angular rate data, and output this to the microcontroller over an SPI connection.

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