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Pneumatics move beyond 'bang-bang'

Pneumatics move beyond 'bang-bang'

Peter Boyer has worked in the fluid power field, developing and manufacturing pneumatic and hydraulic actuators for 30 years. He has been with Bimba Manufacturing since 1981 and has had roles in product development, manufacturing, and manufacturing engineering. Boyer has served as Bimba's vice president of manufacturing and today serves as the organization's vice president of engineering. In this capacity he is responsible for product engineering and new technology research. He also is the general manager of Bimba's Frankfort, IL division, which develops, manufactures, and markets new products.

Traditional pneumatic systems, which simply shift the movement of actuators until they reach some physical stop, will continue to be very valuable in automation systems-even as positioning and control gain importance.

Design News: Ten years from now, what percentage of pneumatic systems will supply precise positioning?

BOYER: Even in 10 years, the vast majority of pneumatic actuators will still be used to provide motion to fixed positions, or to provide a force for an application. However, as pneumatic positioning capabilities evolve, users will be choosing pneumatic positioning systems to provide motions and forces in applications that are much more flexible than the discrete positioning systems of today. We are encouraged by the interest in pneumatic positioning and expect to see use of this capability grow to 10% of all pneumatic actuator systems.

Q: What technology improvements to cylinders still need to happen to realize that goal?

A: Ongoing development of position feedback devices is essential. They will need to be lower cost, have longer life, and provide greater precision than the devices in use today. We will also require continuing development of the control systems used to regulate pressures and flow rates to the actuators. These developments must include simplifying system set-ups, making the control system more responsive to changes in the application, and reducing control system costs.

Q: How do pneumatic positioning systems overcome the factors caused by the compressibility of air?

A: The application of high-order algorithms in positioning controllers allows these systems to anticipate the effects of air compressibility and counteract many of them. This enables these positioning systems to achieve accuracies that are often surprising. Once the desired position is achieved, a significant "stiffness" can be developed in the system by utilizing available air pressure effectively.

Q: Do cylinders require on-board sensors, or are users better off building their own system?

A: Cylinders don't require on-board sensors if sensors are otherwise built into the application. However, we believe the most cost-effective solution for most applications is to combine the sensor with the actuator. This assures the proper attention has been given to minimizing hysteresis and friction. It also simplifies the user's integration of the system into the application.

Q: Will users need special valves to achieve precise positioning?

A: There are a number of ways being developed to control pneumatic positioning actuators. Some of them utilize special valves and some incorporate conventional pneumatic valves. The key is to develop cost-effective user-friendly control systems. It is important to assure the electronics and logic used in the control system are compatible with the valve technology employed.

Q: Some systems already claim positioning to 0.025 mm. What about the future?

A: Positioning accuracies to 0.025 mm will satisfy a very large part of the market interested in pneumatic positioning. The focus of development in the next decade will be to reduce costs, simplify set-up requirements, and to increase system flexibility. As these developments unfold, we will see a greater use of the concept in all application markets.

Q: What role will field buses play in pneumatic positioning?

A: Today, the value of field buses is in the simplification of wiring and reduction of installation costs. Since pneumatic positioning is best implemented with dedicated controllers for each actuator, this technology will benefit greatly from field buses. Field buses will become the backbone that permits these dedicated controllers to synchronize their activities with the needs of the larger system.

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