The final time you put something with your hands, whether or not it was buttoning your shirt or rebuilding your clutch, you used your sense of touch a lot more than you may think. Advanced measurement tools including 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. In fact, 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 surface comparator. It’s a visual tool for analyzing the finish of any surface, however, it’s natural to touch and experience the surface of the part when checking the conclusion. Our brains are wired to utilize the information from not only our eyes but additionally from your finely calibrated Micro Load Cell.
While there are numerous mechanisms by which forces are converted to electrical signal, the primary elements of a force and torque sensor are the same. Two outer frames, typically made from aluminum or steel, carry the mounting points, typically threaded holes. All axes of measured force can be measured as one frame acting on the other. The frames enclose the sensor mechanisms and any onboard logic for signal encoding.
The most frequent mechanism in six-axis sensors is the strain gauge. Strain gauges include a thin conductor, typically metal foil, arranged inside a specific pattern over a flexible substrate. Because of the properties of electrical resistance, applied mechanical stress deforms the conductor, which makes it longer and thinner. The resulting improvement in electrical resistance could be measured. These delicate mechanisms can easily be damaged by overloading, since the deformation of 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 through the design in the sensor device. As the ductility of metal foils once made them the standard material for strain gauges, p-doped silicon has proven to show a significantly higher signal-to-noise ratio. Because of this, semiconductor strain gauges are becoming more popular. For example, all of ATI Industrial Automation’s six-axis sensors use silicon strain gauge technology.
Strain gauges measure force in one direction-the force oriented parallel towards the paths within the gauge. These long paths are made to amplify the deformation and therefore the modification in electrical resistance. Strain gauges usually are not responsive to lateral deformation. Because of this, 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 example, Robotiq made a patented capacitive mechanism at the core of its six-axis sensors. The goal of developing a new form of Rotary Torque Sensor was to create a approach to look at the data digitally, rather than as 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 resistant to external noise. Comparatively, capacitance tech is fully digital. Our sensor has almost 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 are going to represent as being a spring. When you apply a force towards the movable tool, the spring will deform. The capacitance sensor measures those displacements. Understanding the properties from 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 potential for advanced touch and force sensing on industrial robots is obvious. Force and torque sensing already is within use in the area of collaborative robotics. Collaborative robots detect collision and can pause or slow their programmed path of motion accordingly. This will make them capable of working in contact with humans. However, a lot of this sort of sensing is carried out via the feedback current from the motor. If you have an actual force opposing the rotation of the motor, the feedback current increases. This modification can be detected. However, the applied force wbtbtc be measured accurately applying this method. For further detailed tasks, 3 Axis Load Cell is necessary.
Ultimately, industrial robotics is all about efficiency. At industry events and then in vendor showrooms, we percieve a lot of high-tech features created to make robots smarter and more capable, but at the base line, savvy customers only buy as much robot because they need.