Strain Gages Force/Torque Sensors and Cobots in the New “Normal”

Let’s face it, with all the recent restrictions and limitations it’s becoming harder to fill manufacturing positions and to staff medical facilities while ensuring the safety and health of the workers and staff, especially on the frontlines. Using cobots can alleviate worker safety concerns during what may be the beginning of a new “normal” based on social distancing. A cobot can also reduce production costs, increase productivity of the production lines, and engage your team in an era of social distancing and video conferencing.

As COVID-19 is creating new challenges in manufacturing, some manufacturers are innovating their processes during this pandemic and adopting new automation tools to maintain or increase production while keeping their employees as safe as possible.

Reinventing the wheel in manufacturing processes while increasing capacity and maintaining an acceptable level of safety for their workers is not a trivial task, especially without affecting production quality and throughput. One increasing attractive technique is to use robotic devices that are made to work in collaboration with humans. Utilizing force sensing abilities, the strain gage sensors from Micro-Measurements are an important component in the design of the robotic devices that are used to measure directly forces for the robot.

The principle of using a cobot is to re-create a co-worker, new collaborative robots, in critical production stages such as:

• Pick-and-place.

• Quality Testing.

• Machine tending.

• Assembly, Packaging.

• Conveyor line weighing and overload monitoring.

• Hazardous material handling.

• Hazardous environment equipment monitoring to prevent operational failures by monitoring for system limits including torque (binding), thrust (system overload) and bending (improper alignment issues).

As (“Advanced Sensors” *) cobots become ever more common, and as their industrial applications grow in scope, variety, and complexity, so does the need for strain-gage-based transducers feedback in these devices.

The new generation of cobots based strain gage force/torque sensors provide manufacturers with a way to tackle the long-standing issue of worker retention. Cobots will allow production supervisors to reassign workers to more interesting tasks, while the cobots take over the boring and dirty jobs such as heavy lifting or pick and place operation. Cobots can also support social distancing demands.

Using built-in Advanced Sensors Technology strain gage force sensors that detect impact and unusual forces, cobots can operate safely and efficiently without risk of overloading. The Advanced Sensors Technology strain gage force sensors play a vital role not only in force gripping and weighing limit of smart cobots but also in reliably monitoring the obstacles around them. The new cobots based on strain gage sensors are capable of sensing several external forces applied to their frame thanks to on-mounted internal force sensors.

Similar to many other fields of test and measurements, the field of robotics based on strain gage force/torque sensors  also uses the concept of the “last microstrain” (µε).  In cobots, “the last microstrain” describes the great challenge of ensuring that a deployed cobot operates in a safe manner and can be controlled right down to the last microstrain.

Transducer Class® multi-grid advanced strain gage sensors are designed to facilitate reliable, accurate, cost-effective multi-axis force, torque/axial and torsional load measurements within the robot. They may be further used to convert automotive components into force sensing devices.

For example: The design of the Micro-Measurements S5060 Series incorporates VPG’s own proprietary Advanced Sensors Technology, from which a specialty arrangement of both shear and axial half-bridge circuits is configured and installed with a common carrier backing. Customers can choose from among multiple resistance values and gage patterns, in support of a diverse array of bending, torque/shear and thrust measurements.

(*) Advanced Sensors Technology applies tangible specification and manufacturing process improvements, along with industry-exclusive strain gage sensor design techniques, for direct customer benefit. The innovation behind Advanced Sensors Technology reflects many decades of Micro-Measurements R&D experience, gained across a global portfolio of thousands of successful applications, with other refinements achieved via ongoing customer feedback. Strain gage (strain gauge) technology, as a key internal component of finished sensor designs, is a long-recognized industry standard. The strain gages are used to detect a change in electrical resistance, occurring in response to an applied force. In addition to their reliability, strain gages are relatively compact and low cost. This has facilitated their widespread adoption into many of today’s force, load, position, pressure, tension, weight, and strain sensor designs. Such traditional designs have typically called for the bonding and soldering of anywhere from one to four individual strain gages within a single proprietary configuration. Among these, the full Wheatstone bridge, a four-strain-gage arrangement, has consistently offered the highest measurement accuracy, sensitivity and extraneous temperature cancellation. Further design improvements over traditional strain gage types include smaller and tighter grid-resistance tolerances, improved gage-to-gage repeatability, and enhanced measurement stability. All enhancements are implemented via a fully optimized fabrication process, incorporating the very latest in tooling, methods, and equipment. As a result, the prototype design and manufacturing of anywhere from a single strain gage piece up to OEM volumes may be easily accommodated, with uniform high quality and competitive lead times.