The ERDP Remote Drive is a closed-loop system that captures energy and enables more efficient designs.
Air leakage is an accepted challenge in pneumatics applications. It is considered unintentional and requires maintenance and continuous monitoring. However, pneumatic systems are also designed for frequent intentional air releases as part of regular operation, which exhausts usable energy and wastes money.
“A pneumatic actuator is pretty much a set of air tanks on either side of a movable piston within a cylinder,” said Matt Williams, the innovation, technology, and commercialization lead at PHD. “After compressed air is introduced into the cylinder to move the piston, the volume behind that piston still contains energy. If we exhaust the air on the next cycle to move the piston in the opposite direction, all that energy is removed from the system.”
PHD is commonly known as a fluid power actuator manufacturer and solution provider. Yet, its customers grew concerned about energy usage and reducing associated operating costs and carbon footprints and began requesting electrically driven actuators. Though pneumatic actuators typically have higher power density, actuate faster, and produce more force than electrically driven counterparts, energy losses result in sunk costs and increase the system’s carbon footprint.
“We needed to figure out a way to remove the energy in the otherwise exhausted air as the key to gaining energy efficiency in a pneumatic system,” said Williams. “So, we asked ourselves, as engineers and solution providers, how can we maintain the benefits of a fluid power actuator system while reducing those energy losses?”
If PHD decided to convert its technologies and substitute electrical components for pneumatics, it would have to redesign almost all its products. This would incur significant investments for the company and its customers, who would have to requalify the products for their applications.
To solve the problem on all fronts, Williams’ team developed the PHD ERDP Remote Drive as an electrified option and point-of-use alternative. The ERDP forms a closed system to recycle energy in the exhaust air. It comprises two opposing cylinders with pistons, each connected to one actuator port. When the remote drive cycles, it compresses air on one side and expands it on the other without exhausting any air.
“If you think about an actuator, we inject compressed air on one side of the piston, and on the other side, we exhaust. Now, traditionally, we exhaust back to the ambient environment, and then we lose all the energy from the previous cycle’s compressed air,” said Williams. “Instead, we bring the compressed air into the exhaust side of the remote drive and extract that energy. The pressure it has provides a force that acts against a piston, and that force is transferred over to the side doing the air compression. If you want to reverse the direction of the actuator, we just reverse the direction of the remote drive.”
The remote drive uses atmospheric air and seals when it begins to operate. However, it will automatically “take a breath” if it ever needs more air.
“We know air leaks out sometimes, regardless of how well the actuator or system seal is,” said Williams. “So, at the end of each cycle, for a brief period, we breach the piston and open the cavity to ambient air. If we’ve lost any air on the prior cycle, a partial vacuum forms when we return the piston back to its original position. And that partial vacuum, if it exists, if the leak has occurred, pulls in whatever quantity of air from the atmosphere it needs to replace the amount of air lost. If there’s no lost air, if you have a well-sealed system, the system remains completely closed, and we never add any air. But if you leak a little air, we add only a little air to compensate. If you leak a lot of air, we add a lot of air to compensate. And that’s all done automatically by the physics within the system.”
The assembly consists of the drive, controller, motor power supply, and regeneration clamp. Machine builders add their own power supply, PLC cables, air lines, fittings, and actuators. Though the ERDP has one set of actuator ports, machine builders can drive multiple actuators in parallel so that they move in the same direction simultaneously. Alternatively, they can add valves between the remote drive and multiple actuators to drive them sequentially.
Not knowing what the market would demand from this new technology, the company selected a starting point based on customer inquiries. It offers a standard ERDP 54 customizable unit based on the application’s actuators, displacement, and desired pressure.
“We’ve targeted the range of actuators predominantly used for end-of-arm tooling applications, but we can scale that technology and make bigger or smaller units,” said Williams. “For instance, we’re working on a very large unit for a major automotive manufacturer that is driving a robot about the size of a piece of Earth-moving equipment and driving multiple actuators at the end of about a 20-ft robotic arm. In this case, the unit becomes big and is about 75 lb worth of weight. So, we can tailor the technology for the load.”
The technology can also be used in industrial and medical applications, food processing, and nearly any picking operation that uses pneumatic actuation. Mobile robots with grippers are just one of many candidates that can benefit.
“Typically, the only piece of pneumatic equipment on mobile robots is the end effector, and they need that for force and speed. So, they’re stuck having an air compressor on the unit solely to drive that particular actuator. Everything else is electrified already,” said Williams. “If we can replace that air compressor with the remote drive and gain some energy efficiency, we can obviate their need for compressed air.”
Williams also noted that when comparing pneumatic and electric actuators, electric ones are typically heavy and have their mechanisms exposed, whereas pneumatic actuators save significant capacity in size and weight. Plus, the ERDP generates equal force and increases longevity at much less cost than an electric actuator.
“If you think about an end-of-arm application, if I add more weight to the end effector, I’m subtracting that weight from the payload capacity of the robot,” he said. “So, we take the motor, which is the heaviest part of the whole system, both for the remote drive, but also for a typical fully electrified actuator, we offboard that, remove it from the actuator, and we place it somewhere not on the end of the robot arm.”
The ERDP can also function as a vacuum to create suction. For instance, instead of using a venturi pump, which is typically regarded as energy-inefficient, engineers can add check valves to the remote drive to create pressure and generate a vacuum.
Overall, the remote drive is positioned to save energy, costs, and carbon footprint while creating more flexible design options for engineers and machine builders. PHD has plans to continuously advance and optimize this new product to enable more lightweight, energy-efficient design options.
PHD
phdinc.com
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