Robot Nav with Acoustic Delay Triangulation

Building a robot is a rite of passage for electronics engineers. And thus this magazine has published dozens of robotics-related articles over the years.

In the March issue, we present a particularly informative article on the topic of robot navigation in particular. Larry Foltzer tackles the topic of robot positioning with acoustic delay triangulation. It’s more of a theoretical piece than a project article. But we’re confident you’ll find it intriguing and useful.

Here’s an excerpt from Foltzer’s article:

“I decided to explore what it takes, algorithmically speaking, to make a robot that is capable of discovering its position on a playing field and figuring out how to maneuver to another position within the defined field of play. Later on I will build a minimalist-like platform to test algorithms performance.

In the interest of hardware simplicity, my goal is to use as few sensors as possible. I will use ultrasonic sensors to determine range to ultrasonic beacons located at the corners of the playing field and wheel-rotation sensors to measure distance traversed, if wheel-rotation rate times time proves to be unreliable.

From a software point of view, the machine must be able to determine robot position on a defined playing field, determine robot position relative to the target’s position, determine robot orientation or heading, calculate robot course change to approach target position, and periodically update current position and distance to the target. Because of my familiarity with Microchip Technology’s 8-bit microcontrollers and instruction sets, the PIC16F627A is my choice for the microcontrollers (mostly because I have them in my inventory).

To this date, the four goals listed—in terms of algorithm development and code—are complete and are the main subjects of this article. Going forward, focus must now shift to the hardware side, including software integration to test beyond pure simulation.

SENSOR TECHNOLOGY & THE PLAYING FIELD
A brief survey of ultrasonic ranging sensors indicates that most commercially available units have a range capability of 20’ or less. This is for a sensor type that detects the echo of its own emission. However, in this case, the robot’s sensor will not have to detect its own echoes, but will instead receive the response to its query from an addressable beacon that acts like an active mirror. For navigation purposes, these mirrors are located at three of the four corners of the playing field. By using active mirrors or beacons, received signal strength will be significantly greater than in the usual echo ranging situation. Further, the use of the active mirror approach to ranging should enable expansion of the effective width of the sensor’s beam to increase the sensor’s effective field of view, reducing cost and complexity.

Taking the former into account, I decided the size of the playing field will be 16’ on a side and subdivided into 3” squares forming an (S × S) = (64 × 64) = (26, 26) unit grid. I selected this size to simplify the binary arithmetic used in the calculations. For the purpose of illustration here, the target is considered to be at the center of the playing field, but it could very well be anywhere within the defined boundaries of the playing field.

Figure 1: Squarae playing field (Source: Larry Foltzer CC260)

ECHOES TO POSITION VECTORS
Referring to Figure 1, the corners of the square playing field are labeled in clockwise order from A to D. Ultrasonic sonar transceiver beacons/active mirrors are placed at three of the corners of the playing field, at the corners marked A, B, and D.”

The issue in which this article appears will available here in the coming days.

Solid-State Lighting Solutions Project

Electronics system control, “green design,” and energy efficiency are important topics in industry and academia. Here we look at a project from San Jose-based Echelon Corp.’s 2007 “Control Without Limits” design competition. Designers were challenged to implement Pyxos technology in innovative systems that reduced energy consumption. Daryl Soderman and Dale Stepps (of INTELTECH Corp.) took First Prize for their Solid State Lighting Solutions project.

The Pyxos chip is on the board (Source: Echelon & Inteltech)

So, how does it work? Using the Pyxos FT network protocol, this alternative lighting project is a cost-effective, energy-efficient solution that’s well-suited for use in residential, commercial, or public buildings. You can easily embed the LED lighting and control system—which features SSL lighting, a user interface, motion detectors, and light sensors—in an existing network. In addition, you can control up to five zones in a building by using the system’s fully programmable ESB-proof touchpad.

Another view of the Pyxos chip is on the board (Source: Echelon & Inteltech)

 

For more information about Pyxos technology, visit www.echelon.com.

This winning project, as well as others, was promoted by Circuit Cellar based on a 2007 agreement with Echelon.

 

 

 

Improved Radiation Meter Webinar

Want to learn about Elektor’s improved radiation meter? On February 16, Elektor technical editor Thijs Beckers will host a webinar at element14 about the radiation meter, which is a DIY system that can measure alpha, beta, and gamma radiation.

(Improved Radiation Meter – Source: Elektor.com)

According to Elektor, all that’s required to measure radiation is “a simple PIN photodiode and a suitable preamplifier circuit.” The system features “an optimized preamplifier and a microcontroller-based counter. The microcontroller takes care of measuring time and pulse rate, displaying the result in coun

ts per minute.The device we describe can be used with different sensors to measure gamma and alpha radiation. It is particularly suitable for long-term measurements and for examining weakly radioactive samples.”

Its FREE to register at www.element14.com/community/events/3185.

Start Time: 2/16/12 9:00 AM CST (America/Chicago)
End Time: 2/16/12 10:00 AM CST (America/Chicago)
Location: Online event

Elektor International Media is the parent company of Circuit Cellar.