HAMNET Report 23rd June 2024

I am very relieved to realize that we are now past the winter solstice, and our days are starting to grow longer again. Not by very much, mind you. It will take another 3 or 4 days before our Cape Town days last longer than 9 hours and 54 minutes, but every day counts.

Extreme weather is being reported from the Middle East, where very high temperatures of up to 50 degrees Celsius have been experienced during this year’s Hajj pilgrimage to Mecca in Saudi Arabia. More than 1000 pilgrims have died during the extreme heat, and the weather shows no sign of abating.

Similar temperatures eastwards as far as India have also been experienced, with deaths due to heatstroke being reported, and these support the assertion of several aid organizations in America, that have appealed to FEMA to accept extreme heat as being equally as disastrous as floods and storms.

The first Tropical Cyclone of the American Hurricane season has reared its head, as storm ALBERTO passed the coast of Texas this weekend and arrived on Mexico’s coastline. States of disaster were declared in 51 of Texas’ counties as the storm passed by. Strong winds are accompanying the rain and Guatemala and Belize are also in the storm’s aim.

According to the UN, heavy rainfall and strong winds associated with ALBERTO have impacted Guatemala, Nicaragua, Honduras and El Salvador. In addition, media report four fatalities in Nuevo León state, north-eastern Mexico.

The cyclone coincides with the ARRL Field Day weekend, so there will be lots of amateurs on the air, and perhaps helping to convey storm traffic to the National Hurricane Centre. Fortunately the storm is not very severe in strength at present, with wind speeds in the 90km/h range, but about 17 million people are in its path and will experience severe weather.

As you listen to this bulletin, Field Day will still be in progress, and the American Press has been loaded with articles about local radio clubs who will be operating and advertising the hobby. This is good, because it does make the general public aware of the sport and our capabilities, and perhaps encourage newcomers to take their exams and earn a call sign.

The ARRL for example reports that a dozen New Hampshire Amateur Radio Emergency Service (ARES) operators from the Mount Washington Valley ARES group and the Central New Hampshire ARES group, as well as a number of out-of-state ARES volunteers, again provided emergency radio communications at the Delta Dental Mount Washington Road Race on June the 15th.

Fourteen hundred participants ran up the mountain into a region of infamous wind chill and low visibility.

“We were there to keep our eyes open for any runners having physical difficulties, or medical issues,” said Skip Camejo, AC1LC, Public Information Coordinator for the ARRL New Hampshire Section and Public Information Officer for the New Hampshire ARES.

“This could have been done with cell phones, of course, but you can’t count on having a good signal on Mount Washington. That’s why the radio operators will be back for the August bike race up the mountain,” added Camejo.

The ARES help is also considered to be preparation for ARRL Field Day, this weekend, when more than 35,000 radio amateurs gather with their clubs, groups, or simply friends to operate from remote public locations.

Techxplore.com is reporting this week that, successfully to complete missions in dynamic and unstructured real-world environments, mobile robots should be able to adapt their actions in real-time to avoid collisions with nearby objects, people or animals.

Most existing approaches to prevent robot collisions work by creating accurate maps of the environment a robot is navigating and then planning the best trajectories to safely reach a desired location, beforehand.

Many previously proposed robot navigation techniques have achieved promising results in simulation. However, they often did not perform as well in real-world environments, particularly those that are unpredictable and rapidly changing over time.

Researchers at the University of California, San Diego recently introduced a new method that could enhance the navigation of mobile robots in dynamic and unstructured environments.

This method, introduced in a paper posted to the arXiv preprint server, has so far been successfully applied to the Jackal robot, a wheeled robotic system developed by ClearPath Robotics.

“Our recent paper addresses the critical need for safe autonomous navigation of mobile robots in complex, unknown and dynamic environments, while considering the limited sensing and computational resources available on-board,” Kehan Long, co-author of the paper, told TechXplore.

“While previous research has made significant advances using techniques such as artificial potential fields, navigation functions, and control barrier functions, many of those methods rely on constructing an accurate map of the environment.”

Building maps of dynamic environments in real-time can be challenging, particularly if these environments rapidly change over time. The key objective of the recent study by Long and his colleagues was to develop a new method that can guarantee the safety of mobile robots in these changing environments, directly leveraging data collected by a robot’s on-board sensors instead of reconstructing precise maps of the environment.

“Our novel method for safe mobile robot navigation introduces a distributionally robust control barrier function (DR-CBF) formulation,” Long explained.

“The core concept is directly to incorporate the robot’s noisy range sensor measurements (e.g., from LiDAR) into the control optimization as safety constraints, rather than first constructing an accurate map. By employing rigorous theories from distributionally robust optimization, we can robustly account for uncertainties in both sensing and the dynamic environment.”

The mobile robot navigation method developed by Long and his colleagues has various advantages over other approaches introduced over the past few years. Most notably, it can guarantee the safe operation of robots, preventing them from colliding with objects, while only requiring limited computational resources.

“A distinctive feature of our method is that it ensures safe navigation by directly utilizing recent sensor data in determining the control input, enabling the robot to swiftly adapt to environmental changes,” Long said.

“The practical implications of our work are significant. By enabling the development of reliable mobile robots with reduced computational requirements, our approach has the potential to lower the cost of building robots, making them more accessible for a wide range of applications.”

To test their method, Long and his colleagues applied it to the ClearPath Jackal, a wheeled weatherproof robot, which was equipped with a LiDAR sensor. Their findings were encouraging, demonstrating the effectiveness and versatility of their approach in both indoor and outdoor dynamic settings.

“In our future research, we plan to extend our methodology to more complex robotic systems, such as legged robots and humanoids,” Long added. “Our ultimate goal is to develop safe and capable robots that can navigate and interact in any environment while providing robust safety guarantees.”

This is Dave Reece ZS1DFR reporting for Hamnet in South Africa.