The 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 may think. Advanced measurement tools such as gauge blocks, verniers and also coordinate-measuring machines (CMMs) exist to detect minute variations in dimension, but we instinctively use our fingertips to see 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 your machining world: the top comparator. It’s a visual tool for analyzing the finish of the surface, however, it’s natural to touch and notice the surface of the part when checking the finish. Our minds are wired to utilize the information from not only our eyes but additionally from your finely calibrated torque transducer.
While there are several mechanisms by which forces are changed into electrical signal, the key elements of a force and torque sensor are identical. Two outer frames, typically manufactured from aluminum or steel, carry the mounting points, typically threaded holes. All axes of measured force may 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 definitely the strain gauge. Strain gauges consist of a thin conductor, typically metal foil, arranged in a specific pattern on the flexible substrate. As a result of properties of electrical resistance, applied mechanical stress deforms the conductor, making it longer and thinner. The resulting change in electrical resistance may be measured. These delicate mechanisms can be simply damaged by overloading, because the deformation of the conductor can exceed the elasticity from the material and cause it to break or become permanently deformed, destroying the calibration.
However, this risk is normally protected by the style of the sensor device. Whilst the ductility of metal foils once made them the typical 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 example, all of 3 axis load cell use silicon strain gauge technology.
Strain gauges measure force in one direction-the force oriented parallel for the paths inside the gauge. These long paths are designed to amplify the deformation and so the alteration in electrical resistance. Strain gauges are not sensitive to lateral deformation. For this reason, six-axis sensor designs typically include several gauges, including multiple per axis.
There are a few options to the strain gauge for sensor manufacturers. For instance, Robotiq made a patented capacitive mechanism on the core of their six-axis sensors. The goal of making a new type of sensor mechanism was to produce a approach to look at the data digitally, rather than being an analog signal, and reduce 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 virtually no hysteresis.”
“In our capacitance sensor, there are two frames: one fixed and one movable frame,” Jobin said. “The frames are attached to a deformable component, which we will represent as a spring. When you use a force to nanzqz movable tool, the spring will deform. The capacitance sensor measures those displacements. Knowing the properties of the material, you can translate that into force and torque measurement.”
Given the value of our human sensation of touch to our own motor and analytical skills, the immense possibility of 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 will pause or slow their programmed path of motion accordingly. This makes them able to working in contact with humans. However, much of this type of sensing is carried out through the feedback current of the motor. If you have an actual force opposing the rotation from the motor, the feedback current increases. This transformation could be detected. However, the applied force should not be measured accurately using this method. For additional detailed tasks, load cell is necessary.
Ultimately, industrial robotics is about efficiency. At industry events and then in vendor showrooms, we see a lot of high-tech bells and whistles designed to make robots smarter and more capable, but on the financial well being, savvy customers only buy the maximum amount of robot because they need.