Developing a Mobile Assembly Robot for Hazardous Environments With CompactRIO and ROS

Author(s):

Dr. Hamid Roozbahani - Lappeenranta University of Technology
Prof. Heikki Handroos - Lappeenranta University of Technology

Introduction

Founded in 1969, Lappeenranta University of Technology (LUT) is a pioneering institution in Finland that brings together the fields of science and business. The LUT international community includes approximately 6,000 students and experts engaged in scientific research and academic education.

The Intelligent Machines group at LUT carries out research on mechatronic machine design, especially using virtual technologies and simulators, and demanding industrial robotics. The group has participated in significant international research projects and has collaborated extensively with industrial partners.

We have a long tradition of harnessing student assignments to create solutions for new, leading-edge industry areas. These new areas offer many opportunities to discover and trial innovative techniques and systems, while end-users are not that committed to the existing ones. Example applications include virtual racing and horse riding simulators, providing genuine motion feedback. These mechatronic systems develop innovative techniques, which can easily be applied to more conventional industrial applications.

Engineering Solutions to International Challenges

In 2011, an earthquake off the Pacific coast of Japan triggered a powerful tsunami that caused a major disaster at the Fukushima nuclear power plant. The tsunami disabled the emergency power to the reactor cooling systems, which led to three nuclear meltdowns, chemical explosions, and the release of radioactive material.

To prevent further catastrophe, 50 volunteer technicians ventured into the exclusion zone surrounding the power plant to stabilize the reactors. These brave individuals, known as the ‘Fukushima 50’, had to perform simple repair work, including closing valves, in one of the most hazardous environments on Earth. The exposure to extreme radiation could have serious ramifications on their long-term health.

Like many people around the world, our team felt inspired by the Fukushima 50. We admired their bravery, yet felt that modern mechatronic systems could remove the need for humans having to perform menial repair work in such hazardous environments. This became the inspiration for our work on the mobile assembly robot.

Introducing TIERA

TIERA is a versatile, mobile robot that can conduct repair and assembly operations in hazardous areas. The functionality and composition of the robot are defined by the tasks we expect it to perform and the harsh environments we expect it to work in. We considered many environmental factors in our design including radiation, corrosion, toxicity, explosion, biohazard, high voltage, and extreme temperatures.

High mobility was another key design feature for enabling the traversal of hazardous environments. This contrasts with most industrial robots, which are usually stationary and consist of a jointed arm attached to a fixed surface. We had to carefully consider how to make it possible for an expert operator to remotely control the robot from a safe location, and subsequently designed the sensory, communication (WiFi and 4G), virtual reality, and haptic feedback systems required for intuitive teleoperation.

Additional key features of TIERA include:
     • Fanless embedded computer controlling most of the robot’s hardware
     • Robotic manipulators and tools perform various repair tasks
     • Vision system allowing operator to receive video feedback from robot’s cameras
     • Sensors for getting information about the surrounding environment

Strengthening Our Initial Control System

In the beginning of the project, the control system of the whole robot was a Linux-based distribution of the Robot Operating System (ROS), running on an Advantech industrial computer. We quickly learned that the industrial controller alone was not enough to satisfy the needs of our project. Therefore, our team decided to use CompactRIO as the main control system based on NI Linux Real-Time in communication with ROS. This new control architecture provided a super powerful system, which increased our robot controllability to very high accuracy with very low latency.

A complete list of TIERA’s motion, sensory, and control systems:

Why NI?

The CompactRIO platform features integrated software, a range of performance and form factor options, and extensive I/O to reduce risk, boost system performance, and simplify the design of advanced embedded control and monitoring systems.CompactRIO controllers deliver the latest advancements in processing and heterogeneous computing elements, so we can execute advanced control algorithms with deterministic response times and low latency. In addition, various C Series I/O modules provided us with measurement-specific signal conditioning, built-in isolation, and high-performance A/D converters so we could acquire high-fidelity signals.

We eliminated the need for separate subsystems by connecting to sensors, displays, cameras, motors, databases directly to the CompactRIO controller. We then used the LabVIEW graphical environment to define how the CompactRIO handled all this data. We used LabVIEW to program the embedded and FPGA processors within the CompactRIO despite our limited working knowledge of hardware description languages. We used built-in LabVIEW functions to intuitively manage timing and memory, and simplified the development of our signal processing, analysis, control, and mathematical routines.

We used built-in drivers and APIs to move data between components so we could focus on robot development. This means we could spend less time worrying about how to collect data, and more time analyzing and acting on it to ensure the uptime of critical components.

Furthermore, the extensible LabVIEW architecture used by our team ensures that the system can be easily customized and reconfigured through software—even after deployment.

An Innovative Approach to Centralized Robot Control

The main feature of TIERA’s central control system is integration of NI Linux Real-Time and CompactRIO with the flexibility and features of ROS, which generated many novel features for our robot.

Digital communication plays a vital role in any advanced robot. It can include communication between an operator and a robot, between a robot’s control devices and its peripheral hardware, between different programmatic nodes being executed by a robot’s processor, and much more.

A local net allows the transmission of control messages for movement of robot sections, which are published into ROS topics by the main station. Then an onboard computer subscribes to topics and reads messages. From the computer installed on the robot, a signal spreads to each device according to instructions. Signals from a remote control reach the main station, and then they are processed in ROS and sent to the Advantech by WiFi.

We calculated direct and forward kinematics in ROS on the main station and generalized coordinates for control reach controllers inside mechanisms. As explained before, the robot sections operate under control of ROS and we programmed some of them using LabVIEW software. We can merge code from each part together into the one control program, which monitors and controls every device of the robot. We placed controllers of those devices into the one local network, which makes communication between all of them possible.

We can integrate the CompactRIO controller into the whole robotic system using the LabVIEW library to publish information into ROS topics in the same local net.The LabVIEW application runs on the CompactRIO and on the main station at the same time. The user interface translates information from sensors, and we can use the same information after publishing into topics at the same time for other sections of robot. For example, wheels must be stopped if distance to an obstacle is less than a critical threshold.

The ROS and LabVIEW collaboration empowers us to use different types of devices and controllers connected to the one network. We must organize the system in the same network for design of the united system of various groups of hardware and software.

The Future of TIERA

We are making rapid progress with the TIERA robot. All of the robot’s systems are fully operational, and we have tested them individually. We are now commencing the first full system tests and planning further upgrades.

The versatility and modularity of the TIERA and its CompactRIO controller means that it is not limited to assembly and repair in hazardous environments. We can quickly repurpose the robot for multiple industries and other spheres of human activity, including:
     • Hospitals: drug delivery, transportation of food and medicine
     • Cleaning: automatic cleaning of large areas, such as supermarkets, airports, industrial sites
     • Warehouses, Distribution, and Logistics: efficient relocation of materials from stocking shelves to order fulfillment zones
     • Industry: assembly, materials delivery
     • Military and Security: diffusion of explosives, providing vision and monitoring in dangerous areas
     • Mining: exploration of the mines, operation in hazardous areas
     • Ship Yards: performing welding and cutting
     • Research: volcanic research, Antarctica and Arctic research

Author Information:

Dr. Hamid Roozbahani
Lappeenranta University of Technology
P.O. BOX 20 / PL 20
FI-53851 Lappeenranta
Finland
hamid.roozbahani@lut.fi