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VGV / AGV Safety Is, and Will Always Be, in the Driver's Seat

July 23, 2014  |  Jeff Christensen

I think the marketing people here at Seegrid forget that I like to stand around in freezing temperatures while big angry people fire pucks at my face at 90 miles an hour. What do I know about staying safe?

Luckily, I don't need to know a lot, and neither do you, because the control system on a Seegrid vision-guided vehicle (automated guided vehicle) is imbued with all of the safety intelligence it needs. By putting safety in the driver's seat, we can keep you out of that seat, and out of danger.

So, how do we do it?

All autonomous systems (robots, VGVs, AGVs, and humans) enjoy some common traits. They must be able to sense things in their environment and then respond by adjusting their behavior. The appropriate response is determined by the data processing system. A person driving a car is using his/her senses to monitor the environment, and directing the car accordingly. These sensors include the eyes, ears (sensing accelerations and sounds), and sense of touch for forces being applied at the steering wheel, and in the "seat of the pants". The bad news is that with people, the central processing unit is easily distracted, and even though the sensors are working perfectly, the appropriate actions are not always carried out.

Seegrid's vision guided vehicles (VGVs) use redundant sets of sensors and processors so that the safety critical functions can never be ignored, even if the vehicle is posting to its social media page.

A Seegrid vehicle has FIVE pairs of eyes giving it a full 360 degree view. Wouldn't you love to have that capability during rush-hour traffic? This view is used for navigating, and keeping the vehicle on course all the time. The "view" from the cameras is used to update the vehicle's position multiple times a second, using a computer that is dedicated to navigating along the desired route. If that navigation computer is interrupted, or distracted for more than 1 second, other onboard computers that are acting as "watch dogs" will stop the vehicle immediately.

In addition, the vehicle is equipped with speed sensors. These are monitored by a dedicated speed controller at over 50 times per second, in order to maintain a steady and controlled speed at all times. A second embedded computer is monitoring the speed of the vehicle, and checking that against the "command" speed, to make sure that the speed controller is functioning properly. If it senses an "over speed" condition, it instructs yet another computer, the safety controller, to shut the vehicle down.


Another continuously running sensor is the Seegrid patented light curtain. The light curtain surrounds the vehicle with an invisible sensing field that can detect objects as small as two inches high in the path of the vehicle. This sensor is continuously operating and updates the central controller 50 times a second. Anytime an object penetrates the light curtain, the central controller instructs the vehicle to stop in a controlled, but immediate fashion.

Aimed out the front of the vehicle is a specialized safety sensor designed for personnel safety. It is a laser scanning device, with redundant internal controls that is used to monitor the path in front of the vehicle for people or other obstructions. The safety sensor is monitored by the central controller, and by a dedicated UL and TUV approved safety controller. If the safety sensor is activated, or if it malfunctions in any way, the vehicle is brought to a complete stop. If the safety controller malfunctions, the vehicle cannot be operated, even manually. The safety controller, navigation controller, motion controller, and central controller are all communicating with each other continuously. The failure of any single one to communicate in a timely fashion will bring the vehicle to a complete stop.

The navigation controller is also aware of the intended path of the vehicle. Knowing when a change in direction, such as when turns are coming, is what allows the turn signals to function on the vehicle. It also means that the vehicle can slow down in preparation for a turn, and limits the speed accordingly based on the radius of the turn. You know, just like that back-seat driver telling you to slow down on the off ramp.

Just like Driver's Ed

Remember driving school, when the instructor had that extra steering wheel and brake pedal on his side of the car? That is how the sensors and computers on Seegrid VGVs operate to insure everyone's safety. A second "brain" is always checking your speed, telling you when to slow down or speed up, but not interfering with you unless you make a mistake. If you do, they can slam on the brakes before you do anything serious. Seegrid's sensors and controls are like that, continuously, and tirelessly, scanning the environment for navigation clues, obstructions, speed limits, making sure the vehicle is operating safely and under control at all times. And while the Seegrid VGV controls are not susceptible to a lack of sleep, or too much partying, all things can fail somehow, so the system is equipped with redundant components that can monitor any defects, and stop the vehicle before anything dangerous happens.

With computers in control of the vehicle at all times, we can be assured that the vehicle will follow the intended route, maintain the right speed limits, avoid all collisions, behave predictably and consistently, and never behave erratically. But if one of those computers does fail, we can also rest assured that the vehicle will not operate until all of the safety and monitoring systems are operating properly. That is because a failure in the safety system is not an option.

Watch the Improve Safety video

Read More:
AGV Safety Benefits of Automation Seegrid Technology