April 2004, Issue 165

Mini Rover 7
Electronic Compassing fo Mobile Robotics

Recent technological growth has yielded some impressive tools for tackling increasingly difficult tasks. The robotics field has been a large beneficiary of these advancements because it encompasses so many disciplines, each heavily dependent on technology. Mobile robot navigation is one particular recipient of recent technological advancements. Accurate and reliable navigation is fundamental to the success of any mobile robotic application.

Navigation is typically given one of the highest, if not the top, consideration when designing an autonomous mobile robot. You have to consider numerous hardware and software options. These days a GPS receiver is one of the first tools that you think about to fulfill your navigational needs. However, the area that many mobile robots operate in is within GPS’s present 3- to 15-m accuracy range.^[1] Even long-range mobile robots still have to maneuver successfully within that 3- to 15-m resolution uncertainty.

Compound these resolution limitations with satellite signal interference, and it becomes clear that a supplemental system is essential. Heading information, along with positional data from other sources, can provide interim position data as well as augment GPS data to resolve higher accuracies.

A magnetic compass has many advantages as a provider of heading information. Compassing is one of the only methods that can provide absolute heading information without external references for calibration. Today’s electronic compasses easily interface with microcontrollers and come with a host of other features like low-power consumption and built-in local distortion correction, such as any other instrument. Compasses have their own uncertainties and issues. Understanding how compasses work, as well as the behavior of the environment that they measure, will better prepare you to manage their uncertainties and best apply the technology to a project like my Mini Rover 7 robot.