Making Sense of Electrohydraulic Controllers

Here's how to match controller to machine for top-notch performance without overpaying. Bosch Rexroth Corp. – Industrial Hydraulics To download a free guidebook on electrohydraulic controllers and proportional valves visit Machine builders and equipment operators sometimes have misconceptions about hydraulic-based motion. Although valued for its ability to move, crush, or lift heavy loads, hydraulics is often not considered exceptionally precise, or able to support complex, synchronized multiaxis operations. The advent of closed-loop electrohydraulic (EH) motion controllers has changed the situation, making practical hydraulically powered equipment that is extremely precise, repeatable, and adaptable. Today, EH controllers come in a variety of platforms with wide-ranging capabilities, so designers need to assess several factors to choose the right one. Start with the application requirements, including motion complexity and the number of controlled axes. Then move on to machine design and operational factors to finalize the decision. Hydraulic motion control is the coordinated control of acceleration, velocity, and position as well as the force or pressure a cylinder or hydraulic motor exerts. Previous-generation machines were typically open loop, sending a simple signal to a directional or proportional valve to control only one of these factors. This limited precision and sophistication, and open-loop systems often required manual fine-tuning that added time and costs to machine commissioning or updating. Closed-loop control adds feedback to the hydraulic circuit. Position and pressure sensors provide real-time data on parameters such as position, its derivatives, and forces. This opens the door to rapid, precise, repeatable and, most importantly, automated position and force control of hydraulic actuators. Open-loop controls are great for simple applications. But evertighter quality requirements combined with demands for faster throughput increasingly make closed-loop motion control the preferred approach. And digital EH controllers offer significant advantages for OEMs and end users alike. They simplify and speed commissioning