The very last time you put something together with your hands, whether or not it was buttoning your shirt or rebuilding your clutch, you used your sense oftouch more than you might 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 discovered 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 notice the surface of your part when checking the conclusion. Our brains are wired to utilize the information from not just our eyes but also from your finely calibrated torque transducer.
While there are many mechanisms in which forces are transformed into electrical signal, the primary elements 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 you frame acting on the other. The frames enclose the sensor mechanisms and any onboard logic for signal encoding.
The most common mechanism in six-axis sensors will be the strain gauge. Strain gauges include a thin conductor, typically metal foil, arranged in a specific pattern over a 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 simply damaged by overloading, since the deformation of the conductor can exceed the elasticity in the material and make it break or become permanently deformed, destroying the calibration.
However, this risk is typically protected by the design of the sensor device. Whilst the ductility of metal foils once made them the conventional material for strain gauges, p-doped silicon has shown to show a significantly higher signal-to-noise ratio. For that reason, semiconductor strain gauges are gaining popularity. As an example, most of 3 axis load cell use silicon strain gauge technology.
Strain gauges measure force in a single direction-the force oriented parallel towards the paths within the gauge. These long paths are made to amplify the deformation and so the modification in electrical resistance. Strain gauges 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. As an example, Robotiq made a patented capacitive mechanism in the core of its six-axis sensors. The goal of making a new type of sensor mechanism was to create a way to look at the data digitally, instead of being an analog signal, and lower noise.
“Our sensor is fully digital with no strain gauge technology,” said JP Jobin, Robotiq v . p . of research and development. “The reason we developed this capacitance mechanism is mainly because the strain gauge is not resistant to external noise. Comparatively, capacitance tech is fully digital. Our sensor has almost no hysteresis.”
“In our capacitance sensor, the two main frames: one fixed then 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 sensation of touch to our own 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 field of collaborative robotics. Collaborative robots detect collision and can pause or slow their programmed path of motion accordingly. As a result them capable of working in contact with humans. However, most of this sort of sensing is performed via the feedback current of the motor. If you have a physical force opposing the rotation of the motor, the feedback current increases. This transformation could be detected. However, the applied force can not be measured accurately by using this method. For additional detailed tasks, load cell is required.
Ultimately, industrial robotics is about efficiency. At industry events as well as in vendor showrooms, we have seen lots of high-tech special features created to make robots smarter and more capable, but on the main point here, savvy customers only buy just as much robot as they need.