The last time you put something together with your hands, whether or not this 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 differences 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 your machining world: the outer lining comparator. It’s a visual tool for analyzing the finish of any surface, however, it’s natural to touch and feel the surface of the part when checking the finish. The brain are wired to use the data from not just our eyes but in addition from our finely calibrated torque transducer.
While there are several mechanisms by which forces are converted to electrical signal, the main elements of a force and torque sensor are identical. 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 you frame acting on the other. The frames enclose the sensor mechanisms and any onboard logic for signal encoding.
The most typical mechanism in six-axis sensors will be the strain gauge. Strain gauges consist of a thin conductor, typically metal foil, arranged in a specific pattern over a flexible substrate. As a result of properties of electrical resistance, applied mechanical stress deforms the conductor, making it longer and thinner. The resulting improvement in electrical resistance can be measured. These delicate mechanisms can be simply damaged by overloading, since the deformation of the conductor can exceed the elasticity from the material and make it break or become permanently deformed, destroying the calibration.
However, this risk is usually 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 shown to show a significantly higher signal-to-noise ratio. Because of this, semiconductor strain gauges are gaining popularity. For instance, most of multi axis load cell use silicon strain gauge technology.
Strain gauges measure force in one direction-the force oriented parallel for the paths within the gauge. These long paths are created to amplify the deformation and thus the modification in electrical resistance. Strain gauges usually are not sensitive to lateral deformation. For this reason, six-axis sensor designs typically include several gauges, including multiple per axis.
There are several options to the strain gauge for sensor manufacturers. As an example, Robotiq created a patented capacitive mechanism on the core of the six-axis sensors. The goal of making a new kind of sensor mechanism was to produce a way to look at the data digitally, instead of being an analog signal, and reduce noise.
“Our sensor is fully digital without 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 hardly any hysteresis.”
“In our capacitance sensor, the two main frames: one fixed and something movable frame,” Jobin said. “The frames are attached to a deformable component, which we will represent being a spring. When you use a force to nanzqz movable tool, the spring will deform. The capacitance sensor measures those displacements. Knowing 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 the motor and analytical skills, the immense prospect of advanced touch and force sensing on industrial robots is obvious. Force and torque sensing already is at use in the field of collaborative robotics. Collaborative robots detect collision and can pause or slow their programmed path of motion accordingly. This will make them competent at working in contact with humans. However, a lot of this type of sensing is performed via the feedback current from the motor. When there is a physical force opposing the rotation of the motor, the feedback current increases. This modification could be detected. However, the applied force can not be measured accurately using this method. For more detailed tasks, miniature load cell is necessary.
Ultimately, industrial robotics is about efficiency. At industry events and in vendor showrooms, we have seen plenty of high-tech special features made to make robots smarter and much more capable, but on the financial well being, savvy customers only buy as much robot as they need.