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Controlling Force in Pneumatic Applications

Pneumatic systems are designed to perform specific processes that require controlled application of force. Controlling the force generated by fluid power allows engineers to design systems that can exert the necessary force to achieve desired outcomes. Two common elements used together for controlling force are pneumatic cylinders and load cells.

Pneumatic Cylinders

Pneumatic cylinders use compressed air to generate mechanical force and motion. They consist of a cylindrical chamber (cylinder) with a piston inside that moves back and forth when compressed air is supplied or released. The force generated by the pneumatic cylinder is directly proportional to the air pressure and the effective area of the piston.

There are a few ways that pneumatic cylinders are used to control force:

Air Pressure Regulation – The force exerted by a pneumatic cylinder can be controlled by adjusting the pressure of the compressed air supplied to it. Increasing the air pressure increases the force generated by the cylinder, while decreasing the pressure reduces the force.

Piston Size – The effective area of the piston also influences the force exerted by the cylinder. Larger pistons generate more force for the same air pressure compared to smaller pistons.

Directional Control – Pneumatic cylinders can exert force in both directions (extend and retract) by controlling the direction of airflow to the cylinder. This allows for precise control over the motion and force exerted by the cylinder.

Load Cells

Load cells are sensors used to measure force or weight in a variety of application processes. They usually consist of a metal structure with strain gauges bonded to it. When a force is applied to the load cell, it deforms slightly, causing changes in the electrical resistance of the strain gauges. These changes are measured and converted into a force or weight reading.

Ways that load cells control force include:

Force Measurement – Load cells are used to measure the force applied to a system. In pneumatic processes, load cells can be integrated into the system to measure the force exerted by pneumatic actuators or other components.

Feedback Control – Integrating load cells into a pneumatic system allows engineers to implement closed-loop control mechanisms to regulate the force exerted by the system. The measured force can be compared to a desired setpoint, and adjustments can be made to the system’s operation to maintain the desired force level.

Process Monitoring – Load cells provide real-time feedback on the force exerted by the pneumatic system, allowing operators to monitor and adjust the process parameters as needed to ensure desired performance.

Proportion-Air Force Control

Proportion-Air is an industry expert in force control applications. Our standard electronic proportional valve provides an accuracy of ±0.2 percent of full scale and a repeatability of ±0.02 percent of full scale calibration – precise force is easily achieved.

When applications require a load cell to be used for closed-loop force control, the load cell’s output can be sent directly into a QB2 proportional regulator as second loop feedback. The QB2 does the loop closing for you – it compares your controller’s command signal input with the signal output from your load cell.