The last time you put something together with your hands, whether it was buttoning your shirt or rebuilding your clutch, you used your feeling oftouch more than you might think. Advanced measurement tools such as gauge blocks, verniers and even coordinate-measuring machines (CMMs) exist to detect minute variations in dimension, but we instinctively use our fingertips to ascertain if two surfaces are flush. Actually, a 2013 study learned that the human sense of touch can also detect Nano-scale wrinkles on an otherwise smooth surface.
Here’s another example from the machining world: the surface comparator. It’s a visual tool for analyzing the conclusion of any surface, however, it’s natural to touch and experience the surface of your own part when checking the finish. The brain are wired to make use of the details from not only our eyes but additionally from your finely calibrated torque transducer.
While there are numerous mechanisms by which forces are changed into electrical signal, the key 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 could be measured as one frame acting on the other. The frames enclose the sensor mechanisms as well as any onboard logic for signal encoding.
The most typical mechanism in six-axis sensors is the strain gauge. Strain gauges contain a thin conductor, typically metal foil, arranged in a specific pattern on the flexible substrate. Due to the properties of electrical resistance, applied mechanical stress deforms the conductor, making it longer and thinner. The resulting change in electrical resistance can be measured. These delicate mechanisms can be easily damaged by overloading, as the deformation in the conductor can exceed the elasticity of the material and make it break or become permanently deformed, destroying the calibration.
However, this risk is usually protected by the design of the sensor device. As the ductility of metal foils once made them the conventional material for strain gauges, p-doped silicon has seen to show a lot higher signal-to-noise ratio. For this reason, semiconductor strain gauges are becoming more popular. For instance, most of triaxial load cell use silicon strain gauge technology.
Strain gauges measure force in one direction-the force oriented parallel towards the paths inside the gauge. These long paths are designed to amplify the deformation and therefore the change in electrical resistance. Strain gauges usually are not sensitive to lateral deformation. For that reason, six-axis sensor designs typically include several gauges, including multiple per axis.
There are a few choices to the strain gauge for sensor manufacturers. For instance, Robotiq developed a patented capacitive mechanism at the core of their six-axis sensors. The objective of creating a new form of sensor mechanism was to produce a method to appraise the data digitally, instead of being an analog signal, and lower noise.
“Our sensor is fully digital without strain gauge technology,” said JP Jobin, Robotiq vice president of research and development. “The reason we developed this capacitance mechanism is because the strain gauge is not safe from external noise. Comparatively, capacitance tech is fully digital. Our sensor has almost no hysteresis.”
“In our capacitance sensor, the two main frames: one fixed and one movable frame,” Jobin said. “The frames are affixed to a deformable component, which we are going to represent being a spring. When you use a force to nanzqz movable tool, the spring will deform. The capacitance sensor measures those displacements. Learning the properties of the material, it is possible to translate that into force and torque measurement.”
Given the need for our human sense of touch to our motor and analytical skills, the immense possibility of advanced touch and force sensing on industrial robots is obvious. Force and torque sensing already is in use in the area of collaborative robotics. Collaborative robots detect collision and may pause or slow their programmed path of motion accordingly. This will make them able to working in touch with humans. However, most of this type of sensing is carried out through the feedback current in the motor. If you have a physical force opposing the rotation of the motor, the feedback current increases. This transformation may be detected. However, the applied force can not be measured accurately applying this method. For more detailed tasks, miniature load cell is needed.
Ultimately, industrial robotics is about efficiency. At trade events and in vendor showrooms, we see lots of high-tech features created to make robots smarter and a lot more capable, but on the main point here, savvy customers only buy the maximum amount of robot because they need.