Should Robots Have an Emergency Stop?

Every robot must include an emergency stop button or deadman switch for safety. An e-stop button can shut down a device acting unexpectedly and dangerously, whether it’s a school assignment, a hobby project or an expensive manufacturing plant assistant. Surprisingly, no matter the size and cost of the robot — even if it’s in a science fiction movie — there’s usually no excuse not to have an emergency stop button.

There are optimal placements and designs for the best emergency stop button. It helps functionality and guides the robot on how to act when the stop activates. Here are the details about every option — and a case to not include one.

Where Should the E-Stop Button Go?

If the robot has a deadman switch or emergency stop button, it only makes sense for it to be accessible. It should be easy to press or pull, but not so much that someone can trigger it accidentally. Miniature hobby robots might be stopped by inserting a pin on a button to cut electrical currents. More complex robots need heavier-duty solutions.

Thankfully, commercial robots have strict guidelines for where these buttons should go. Operators that follow them accurately can maintain safety while leaving no room for questioning. It leaves more time to work on other facets, like design and capabilities.

However, robotic operators and designers should work around the e-stop button to maximize its abilities. It must be red for visibility and shaped like a mushroom head for easy pressing. According to compliance, it should be mounted on a slightly elevated yellow background everywhere operators have control over the robot. They should be easy to access — not behind padlocks, keys or security codes. Even hobby robots for fun should have an easy stopping mechanism. 

Everything must be easy to find and operate, so robots stop when expected to prevent further destruction or danger to operators or other machines. The beauty of an emergency stop button is there are always other safety precautions alongside it. It’s never the only go-to. Hopefully, operators will always be aware of the control and rarely employ it — unless it’s for testing.

Push buttons are one of the most common emergency stop mechanisms. Given the environment, there are plenty of others people can use as backup or supplementary measures. For example, a pull or rope cord works best around a conveyor belt. A teach pendant — a handheld device or screen for commanding a robot — can have one built into it.

What Are Stop Categories?

Knowing stop categories assists operators in understanding how the e-stop button works. They’re defined by a few regulatory bodies in the professional world, but at their core, they mean the same things. They all revolve around the actuator — the part that helps with powering robotic movement — and interactivity with the type of motor it has. These are the groups of shutdown methods:

Category 0: An uncontrolled stop, known by immediate power removal from the whole robot
Category 1: A controlled stop, which relies on the actuators to execute, stopping the rest of the machine
Category 2: Another controlled stop that continues to leave power in the actuators

The robot should have an emergency stop button related to the category stop the user wants to achieve. Operators should evaluate the machine’s risk in an emergency to make this decision. 

What’s the Difference Between E-Stop and Lockout Tagout?

A lockout tagout (LOTO) is another robotic stopping protocol. Knowing the difference between crucial operations is essential, whether people are still studying robotics or entering the field for the first time. LOTO isolates hazardous power from entering the machine, shutting down the robot entirely. Operators primarily use it for maintenance, so LOTO is planned.

E-stops are not planned, and sudden stops often harm machinery. More hazardous machines should have Category 0 stop options instead of Category 1 or 2. However, shutting off all power could endanger operators if there are suspended mechanisms that can fail. 
LOTO shuts off power in a controlled circumstance that protects workers and machines instead of potentially endangering or damaging them. Everything boils down to what each robot is capable of, even with just a little power. 

Though Category 0 stops can power down an entire robot, people should not use it as a power-down alternative. They shouldn’t even be used in LOTO scenarios. They have similar outcomes with various power distributions that enable workers to continue working. Using an e-stop button has steps, from readjusting the switch back to the operating position and resetting and powering back on the machines. 

Is There a Case Against an Emergency Stop Button?

Not every robot would benefit from an emergency stop. Therefore, a button or action shouldn’t exist for it. Compliance dictates specific machines need them, while others don’t and rely on a risk assessment from operators. Evaluating robots for these factors identifies how each one can pose threats and how operators can increase safety protocol no matter the design or purpose. 

For example, if stopping the machine abruptly would cause more harm than good, perhaps a Category 0 stop isn’t ideal. It makes sense not to include it if it doesn’t help mitigate or contain the danger. Additionally, the robot shouldn’t have switches if stopping would add new risks. 
Some safety suggestions dictate handheld or portable robots don’t require emergency stop buttons.

These situations are rarer and should make robot enthusiasts question how to increase safety in these circumstances and what complementary protections they can implement. E-stop buttons don’t inherently protect people controlling robots — they only stop machines. This should prompt robotics innovators to incorporate more protective measures to improve robotic operations.

Most Robots Need a Deadman Switch

An e-stop button for robots is a benefit in almost all situations. Rules make it easy for operators and engineers to locate and use them without second-guessing themselves. Every variation empowers robotics enthusiasts and experts to keep exploring safety in the field, but the goal should be to avoid an emergency stop in the first place.

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