Making Mobile Robots Smarter and Safer

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Mobile robots are becoming increasingly common in industry. Many robots rely on sophisticated navigation and anti-collision systems, which can often be bulky, expensive, and computationally demanding. But it doesn’t need to be this way. This article outlines how strategically placed range sensors can offer a flexible, lean, and cost-effective alternative.

Automation increases safety, productivity, quality, and consistency of industrial processes. The role of automation in industry has been growing since the early 1900s and today automation has moved on from machines that perform simple repetitive tasks to industrial robots that absorb information and respond to what is going on around them.1

Reliable Navigation Systems are Essential for Safe, Efficient Mobile Robots

No longer happy standing still, industrial robots are now mobile, which has opened up a whole new set of applications for them. Robots are now taking over tasks like picking up goods and moving them around warehouses, jobs that have typically been done by humans or vehicles driven by humans.1,2

Industrial mobile robots must be able to navigate increasingly complicated, continually changing environments safely and efficiently. To do this, they need to be able to detect obstacles in front of them and make split-second decisions about how to avoid them. No one would want a pizza delivery guy who constantly crashes or aimlessly drives around the neighborhood before handing over a cold pizza. Likewise, people prefer mobile robots that complete their task effectively without bumping into things.2

Sensors Help Robots ‘See’ their Environment

The simplest solution for robot navigation uses collision-based technology where robots detect objects by bumping into them. They then change their direction to avoid the obstacle. This low-tech solution may work for small, simple robots such as robot vacuums, but it’s unlikely to be the best option for robotic forklifts navigating around people and expensive goods.3-5

Ultrasonic sensors transmit sound waves and detect waves that bounce off obstacles and return to the sensor. Ultrasonic sensors can tell a robot that an obstacle is present, but the nature of ultrasonic sensors means that their function is quite limited and error-prone. Their maximum range is often quite short and their updates rates slow.3-5

LiDAR Laser Scanners Provide Precise Positioning – At a Cost

LiDAR (Light Detection and Ranging) laser scanners offer a high-tech solution for robot anti-collision. They operate on the Time-of-Flight principle, where light emitted from the scanner hits obstacles in front of the robot and bounces back to the sensor. The time taken for the light to travel from the source to the object and back to the detector is used to calculate the distance between the robot and the object.3,5,6 Rotating LiDAR systems employ a motor to rotate the sensor or to divert the laser beams to scan their full environment.

Laser scanners provide real-time, precise maps of a robot’s environment, enabling accurate anti-collision and obstacle avoidance even in dynamic situations. However, they are often expensive and provide thousands of data points per second, resulting in a mountain of data that requires significant processing power to analyze. This results in a costly system that consumes a lot of energy.3,5 In addition, laser light can damage human eyes, so laser scanners must be mounted at floor level to comply with safety regulations.

Thoughtfully Placed Distance Sensors Can Provide 3D Coverage at a Fraction of the Price

Using strategically placed distance sensors it is possible to create “selective point clouds” to provide a leaner and more cost-effective solution than conventional environment-scanning ToF technology. This can also be complementary to full environment-scanning and offer redundancy at a fraction of the cost.

With the right sensor configuration, mobile robots can monitor their environment and perform anti-collision using only a few single-point distance sensors, significantly reducing cost and system complexity compared to modelling and interpreting their full 3D environment.

Left: Anti-collision system using a laser scanner, Right: Example of object detection using Terabee sensor arrays.

Figure 1. Left: Anti-collision system using a laser scanner, Right: Example of object detection using Terabee sensor arrays.

Complimentary technology, overcoming bi-dimensional limitations.

Figure 2. Complimentary technology, overcoming bi-dimensional limitations.

TeraRanger Hub Evo - The Flexible Solution for Mobile Robot Navigation

The TeraRanger Evo from Terabee is a ToF sensor that uses eye-safe infrared LED light to measure distances. Recognizing the need for positional flexibility, Terabee has created the TeraRanger Hub Evo. The hub is a small, octagonal board that allows users to connect up to eight TeraRanger Evo distance sensors and place them in whatever configuration they require. The TeraRanger Hub Evo enables you to track multiple angles with a straightforward system. This unrivaled flexibility enables customers to choose which areas and axes to monitor around the robot and the system can be adjusted to different applications. This flexible approach also makes prototyping fast and easy.7,8

Custom sensor arrays with TeraRanger Hub Evo.

Figure 3. Custom sensor arrays with TeraRanger Hub Evo.

TeraRanger sensors use completely eye-safe infrared LEDs as an alternative to laser beams. This means that the sensors can be mounted in more strategic locations than laser scanners, with zero risk of damage to eyesight.

With the TeraRanger Hub Evo, robots can maneuver successfully around warehouses and other industrial settings, avoiding collisions with pallets, machinery, and people.  This simple solution reduces cost, power consumption, size, and weight of the overall system. What’s more, if you already have other technologies in place, the TeraRanger Hub Evo and Evo sensors can add extra functionality and improve safety at a low cost.7,8

References and Further Reading

  1. ‘Industrial Automation and Robotics: An Introduction’ — Gupta AK, Arora SK, Riescher Westcott J, Mercury Learning & Information, 2016.
  2. ‘Introduction to Autonomous Mobile Robots’ — Siegwart R, Nourbakhsh IR, Scaramuzza D, MIT Press, 2011.
  3. ‘Sensors for Mobile Robot Systems’ — Kucsera P, AARMS, 2006.
  4. ‘Performance comparison of Infrared and Ultrasonic sensors for obstacles of different materials in vehicle/ robot navigation applications’ — Adarsh S, Kaleemuddin MS, Bosen D, Ramachandran KI, IOP Conf. Series: Materials Science and Engineering, 2016.
  5. ‘Electronic Sensing Technologies for Autonomous Ground Vehicles: A Review’ — Ilas C, Advanced Topics in Electrical Engineering, 2013.
  6. ‘Time-of-flight principle’ https://www.terabee.com/time-of-flight-principle/
  7. ‘High-performance distance measurement sensor modules’ https://www.terabee.com/sensors-modules/lidar-tof-range-finders/
  8. ‘TeraRanger Hub Evo’ https://www.terabee.com/shop/accessories/teraranger-hub-evo/

This information has been sourced, reviewed and adapted from materials provided by Terabee.

For more information on this source, please visit Terabee.

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