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 a lot 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 check if two surfaces are flush. Actually, a 2013 study found that the human sense of touch may even 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 conclusion of any surface, however, it’s natural to touch and experience the surface of your part when checking the conclusion. Our minds are wired to utilize the data from not just our eyes but in addition from your finely calibrated Micro Load Cell.
While there are several mechanisms by which forces are transformed into electrical signal, the key areas 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 one other. The frames enclose the sensor mechanisms and then 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 within a specific pattern on a flexible substrate. Due to the properties of electrical resistance, applied mechanical stress deforms the conductor, which makes it longer and thinner. The resulting alternation in electrical resistance may be measured. These delicate mechanisms can be easily damaged by overloading, because the deformation from the conductor can exceed the elasticity of the material and cause it to break or become permanently deformed, destroying the calibration.
However, this risk is normally protected by the design in the sensor device. As 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 this reason, semiconductor strain gauges are becoming more popular. For instance, most of 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 in the gauge. These long paths are created to amplify the deformation and therefore the alteration in electrical resistance. Strain gauges usually are not understanding of lateral deformation. For that reason, six-axis sensor designs typically include several gauges, including multiple per axis.
There are some options to the strain gauge for sensor manufacturers. As an example, Robotiq made a patented capacitive mechanism at the core of their six-axis sensors. The aim of creating a new form of Torque Sensor was to make a method to appraise the data digitally, rather than being an analog signal, and minimize 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 because the strain gauge is not really resistant to 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 being a spring. Once you use a force towards the movable tool, the spring will deform. The capacitance sensor measures those displacements. Understanding the properties from the material, you can translate that into force and torque measurement.”
Given the price of our human sense 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 in use in the field of collaborative robotics. Collaborative robots detect collision and will pause or slow their programmed path of motion accordingly. This will make them capable of doing work in contact with humans. However, much of this type of sensing is done through the feedback current in the motor. Should there be an actual force opposing the rotation in the motor, the feedback current increases. This change could be detected. However, the applied force wbtbtc be measured accurately using this method. For additional detailed tasks, Multi Axis Force Sensor is necessary.
Ultimately, industrial robotics is about efficiency. At industry events and then in vendor showrooms, we see a lot of high-tech features made to make robots smarter and more capable, but on the bottom line, savvy customers only buy the maximum amount of robot as they need.