The final time you put something along with your hands, whether it was buttoning your shirt or rebuilding your clutch, you used your sense of touch more than it might seem. Advanced measurement tools such as gauge blocks, verniers as well as coordinate-measuring machines (CMMs) exist to detect minute differences in dimension, but we instinctively use our fingertips to ascertain if two surfaces are flush. In reality, a 2013 study found that the human sense of touch can even detect Nano-scale wrinkles on an otherwise smooth surface.
Here’s another example from the machining world: the outer lining comparator. It’s a visual tool for analyzing the finish of any surface, however, it’s natural to touch and feel the surface of your part when checking the finish. Our brains are wired to utilize the details from not only our eyes but also from your finely calibrated Miniature Load Cell.
While there are many mechanisms in which forces are converted to electrical signal, the primary parts of a force and torque sensor are the same. Two outer frames, typically made of aluminum or steel, carry the mounting points, typically threaded holes. All axes of measured force can be measured as one frame working on another. The frames enclose the sensor mechanisms and any onboard logic for signal encoding.
The most typical mechanism in six-axis sensors is definitely the strain gauge. Strain gauges contain a thin conductor, typically metal foil, arranged within a specific pattern on the flexible substrate. Because of the properties of electrical resistance, applied mechanical stress deforms the conductor, rendering it longer and thinner. The resulting alternation in electrical resistance could be measured. These delicate mechanisms can be easily damaged by overloading, because the deformation in the conductor can exceed the elasticity from the material and make it break or become permanently deformed, destroying the calibration.
However, this risk is normally protected by the design of the sensor device. While the ductility of metal foils once made them the typical material for strain gauges, p-doped silicon has seen to show a significantly higher signal-to-noise ratio. Because of this, semiconductor strain gauges are gaining popularity. As an example, all ATI Industrial Automation’s six-axis sensors use silicon strain gauge technology.
Strain gauges measure force in one direction-the force oriented parallel to the paths inside the gauge. These long paths are created to amplify the deformation and so the modification in electrical resistance. Strain gauges are certainly not sensitive to lateral deformation. For this reason, six-axis sensor designs typically include several gauges, including multiple per axis.
There are several choices to the strain gauge for sensor manufacturers. For instance, Robotiq created a patented capacitive mechanism on the core of the six-axis sensors. The aim of creating a new kind of Rotary Torque Sensor was to create a method to measure the data digitally, as opposed to being an analog signal, and lower noise.
“Our sensor is fully digital with no strain gauge technology,” said JP Jobin, Robotiq vice president of research and development. “The reason we developed this capacitance mechanism is simply because the strain gauge will not be safe from external noise. Comparatively, capacitance tech is fully digital. Our sensor has virtually no hysteresis.”
“In our capacitance sensor, there are 2 frames: one fixed and one movable frame,” Jobin said. “The frames are affixed to a deformable component, which we will represent being a spring. When you apply a force for the movable tool, the spring will deform. The capacitance sensor measures those displacements. Knowing the properties from the material, it is possible to translate that into force and torque measurement.”
Given the price of our human feeling of touch to the motor and analytical skills, the immense prospect of advanced touch and force sensing on industrial robots is obvious. Force and torque sensing already is within use in the field of collaborative robotics. Collaborative robots detect collision and may pause or slow their programmed path of motion accordingly. This will make them competent at employed in contact with humans. However, most of this type of sensing is carried out through the feedback current from the motor. If you have an actual force opposing the rotation of the motor, the feedback current increases. This change can be detected. However, the applied force wbtbtc be measured accurately using this method. For further detailed tasks, Multi Axis Load Cell is necessary.
Ultimately, industrial robotics is all about efficiency. At trade shows and in vendor showrooms, we have seen a lot of high-tech bells and whistles designed to make robots smarter and more capable, but on the bottom line, savvy customers only buy just as much robot because they need.