ROS Basics – challenges in the robotic low cost context

Applications in robotics need to solve a lot of computational intensive tasks. While some of them can be outsourced to an externally powered device like a laptop or a server, others essentially can be calculated on the UGV.

Examples for that are collecting sensor data, receiving and executing commands or streaming data. Balancing these is a challenging task, because on concurrent executing systems all processes can influence each other. Especially when computational power gets cut down to the limits in order to save energy. As most libraries, frameworks or software environments do, ROS requires additional resources when being compared to a single purpose application.

In conclusion providing enough computational power while using reasonable amounts of energy is an important task to solve.

Physical properties
Physical dimensions and requirements result from a tradeoff between costs and size, whereas smaller UGVs tend to be more expensive and complex. On the other hand, an upper bound among others is set by being manageable in terms of transport and storage.

The low cost target UGV is a four wheel or two tracks driven ground robot with physical dimensions below 150mm * 300mm * 300mm (height, width, length). The drive power should be accordingly with an effective force of more than 100 Ncm for moving or holding torque in case of stronger slope. Additionally, tracks are the preferred primary propulsion system as they have better grip properties and only require simple motor control. Another nice to have would be the capability of spot-turning, which would allow operating on small areas and facilitates 3D scans of rooms without moving further than required. Another optional point if the robot is going to be used outside of buildings or around kids is a splash-proof case that would increase the robots life. Furthermore, modular extensibility would increase the usability of the robot significantly.

Modular design

In order to solve the tremendous requirements of robotics in a low cost context, we need to think out of the box while structuring the challenges in solvable problems. Like the following graph shows, we should divide the functionality of UGVs into four main modules: First, Sensors are the parts the robot requires to sense the outside world, next Accumulators serving and saving power, followed by Processors the units are processing information gathered by Sensors and finally, Actuators which provide physical movement. These areas in turn get separated into further sections which we discuss one by one on the next posts.