How Robotic Force Sensors Work
Today’s industrial robots are able to automate more complex applications. Manufacturing processes once deemed impossible for industrial robots are now being converted from manual processes to robotic ones. The development of advanced robotic technologies has expanded the use of industrial robots for simple, repetitive tasks to ones that take great skill. Robotic force sensors are one of the technologies leading the way for the advancement of robots.
Robotic force sensors give robots the sense of touch. Industrial robots integrated with force sensors are able to detect torque and force that is applied to their end-effector or wrist. Integrating the FANUC Lr Mate 200id with force sensors enables it to have a human-like sense of touch and the ability to automate fine-skilled processes. The touch feedback provided through force sensors ensures greater accuracy and product quality.
Most robotic force sensors are integrated with the robot wrist and end-effector since they are needed to measure the force applied to workpieces during their operation. Collaborative robots are built with force sensors in their robotic arm. Cobots, like the FANUC CR-15ia, use force sensors for safety purposes instead of for solely enhancing their operation. Force sensors in cobots are what allow them to operate barrier-free alongside humans.
The general working concept of a robotic force sensor is to measure and respond to applied pressure. When a force sensor detects pressure, it converts the pressure value into a measurable quantity. Most force sensors use resistors to detect and measure force. The resistors base their measurements on contact resistance. The resistors contain a conductive polymer film and electrodes. When pressure is applied to the surface of the sensor, the polymer film changes resistance. Within the film is a matrix of non-conducting and electrically conducting particles. These particles alert the resistor’s electrodes when force is applied, and the electrodes then change the sensor’s resistance.
The type of robotic force sensor will determine the accuracy of the force measured, how it is measured, and where it is detected. There are three types of force sensors that can be integrated with industrial robots; pressure sensors, strain gauge sensors, and capacitive sensors.
Pressure sensors are the most basic and most affordable type of force sensor. These sensors can only detect force applied to a single axis from one direction. Their main purpose is to determine if force was applied as they cannot accurately measure the amount of force.
Strain gauge force sensors consist of single-axis load cells and multi-axis sensors. Multi-axis sensors are the most common for articulated robot integration since they can detect and measure force on all six robotic axes. Integrating a multi-axis strain gauge sensor with the FANUC M710ic/50, enables it to have the sensory touch needed for automating finishing applications. The M710ic/50 through force sensory technology can accurately grind, sand, or buff workpieces resulting in smooth, even finishes while preventing touchups or rework.
Capacitive force sensors are the force sensors of the future as they can measure force digitally instead of through a signal. Their digital capability makes them extremely accurate.