Robotic collision sensors are essentially end-effectors that protect robots from being damaged when they approach an obstruction or contact. Collision sensors operate when a vertical or horizontal force exceeds the programmed limit. There are three main methods to sense contact with an obstruction that will cut off the robot – pneumatic, mechanical, and a combination of mechanical and pneumatic. All signals are fed to the robots control unit, which cuts power to the robot. Noncontact collision sensors are used to help robots avoid collisions.
Mechanical collision sensors are spring-loaded devices that automatically trip when a vertical or lateral force is applied. Typically they activate when the robot comes in contact with an obstruction. Similarly, pneumatic collision sensors trip when a vertical or lateral force is applied, although they are pneumatically actuated. Combination mechanical and pneumatic collision sensors use pneumatics for dynamic compliance. They are usually configured through a combination of springs and regulated air. Noncontact sensors are used for collision avoidance. Theses sensors act like a compliance device and help the robot avoid damaging impacts. In robotic applications this is an emerging technology.
Collision sensors may use any of a number of compliances to signal shut-off. The most common types of compliance are angular, rotary or torsional, and axial. Angular compliance is the distance in degrees from vertical the sensor will allow before signaling the control to shut off. Rotary compliance is the distance in degrees about a point the sensor will allow before signaling the control to shut off. Axial compliance is vertical displacement, positive or negative, in inches or millimeters, the sensor will allow before signaling the control to shut off. Some collision sensors can be set with “pre-trip compliance, which is an adjustable compliance setting where the user determines what is the allowable rate of deflection. Even more advanced devices may have a repeatability feature, which causes the robot to reset to a safe position and travel to that same position consistently.