It is important to understand the operation of the robot. It can be taught to operate within a range, to avoid collision with taught objects, and even prevented from colliding with itself. It is not however aware of you, the operator. It does not know what objects you have placed on the bed. It does not know if your fellow classmates are getting too close.A robot is taught to move to locations determined by the operator. You must always be aware of what is occurring while the robot is in motion, and reduce the risk of collision as much as possible.
In our lab, the primary safety devices are as follows:
- Emergency Stops
- Emergency Stop Buttons are available on the Teach Pendant and the Operator Panel on the robot's controller. Push in to enact an emergency stop, pull out to disable it.
- Operator Presence Control or "DeadMan Switch"
- The FANUC teach pendant's Operator Presence Control is a 3 position switch available on both the left and right back side of the controller. While holding the controller for motion, you will have to press the button in to the middle position to enable motion. Pressing it in two far (past the first "click") will disable it again. Using a properly adjusted wrist strap helps keep your hand steady and in the correct position for the Operator Presence Control.
- Teach Pendant On/Off Switch
- The FANUC teach pendant has an on/off switch located in the upper left. This will allow or prevent modifications to programs and some motion systems. Turning the teach pendant on gives the operator sole control of the robot, meaning external commands will not begin programs or cause motion.
- T1/T2/Auto Mode
- When teaching the robot to perform tasks, we remove it from automatic mode and put it into a speed limited, higher safety mode.
- Distance Sensor
- Directly below the robots is a distance sensor designed to detect the presence of people and objects, to prevent full speed motion when people are within a specific radius. This sensor is only used in AUTO mode, as T1 mode limits motion speed by default.
- Force Sensor
- The robot can calculate payload and its own inertial mass to have a fairly accurate estimation of how much current should result in a desired acceleration and velocity. When the response of the robot arm is outside of expected tolerances for a given motion command, the robot enters a hard stop and applies the brakes. This is triggered often if a tool's DCS parameters have been set incorrectly and the end hits the bed, the arm itself, or the cage. It can also trigger when contacting a person, although not quickly enough to prevent injury.
- The payload can be changed in settings if desired.
- The robot's control panel includes a power disconnect switch that can be locked out in a safe position. This is required during the majority of maintenance tasks involving the robot itself, while the safety circuit should be tied to a lockable device such as a cage door interlock or estop interlock when performing work on other devices within the cell.
- Speed Limits
- On our educational carts, the T1 speed is limited to 250mm/s. If the processor detects speed above this value, the brakes are engaged.
- Cell Cages
- Magnetic Reed Switches on Doors and Panels
- Light Curtains
- Laser Interrupt
FANUC robots contain software and hardware known as Dual Check Safety (DCS) which set limits on the areas in which the robot is allowed to move.
For example, the robot is physically capable of driving the tool to a position in which its own arm is located. Instead of "punching itself" and risking damage, the DCS system prevents it from reaching these positions.
While many robot systems contain similar software limits, FANUC is specifically designed such that known positions and estimated positions are calculated and then compared. If these do not match - then at least one is at fault and an Alarm condition occurs.
Note: If the robot does reach a safety zone, you must set the coordinate system (COORD button) to JOINT, jogging whichever part of the robot that has left the zone back into the designated safe area.
Personal Protective Equipment
As with any situation with powerful or dangerous equipment, PPE is a required component of hazard mitigation.
Personal protective equipment is by far the least effective method of ensuring safety but is a required component none the less. In our lab, closed toed shoes and safety glasses are a necessity. In the field, you will likely encounter requirements of hard-toe shoes, hard hats, and safety vests.