Servo hydraulic cylinder with a piston rod displacement sensor:
To implement closed-loop control of hydraulic systems—such as flow‑rate regulation—it is essential to accurately measure piston‑rod displacement in real time. In particular, for long‑stroke, high‑speed piston cylinders, it is necessary to use servo‑hydraulic cylinders equipped with a precision piston‑rod displacement measurement system.
A. Based on the control requirements of hydraulic systems, many operating conditions necessitate the measurement of piston‑rod displacement. Depending on accuracy and stroke‑length specifications, different methods are employed for measuring piston‑rod displacement in various applications:
- Magnetostrictive displacement sensors, including redundant magnetostrictive sensor assemblies used in critical safety‑control applications, offer a maximum measurement range of 7 to 8 meters; however, they typically achieve higher accuracy within the 1.5‑meter range.
- Pulse sensors constructed from non‑magnetic materials represent a mature solution that offers superior cost‑effectiveness and measurement accuracy. These sensors are typically mounted on the end caps of hydraulic cylinders, where they detect pulses generated by alternating segments of non‑magnetic material affixed to the piston rod, thereby providing precise displacement signals. This piston‑displacement sensing approach is easy to install and boasts the advantage of measurement accuracy that remains unaffected by the magnitude of the measured displacement, making it highly promising for future applications.
- A non-contact laser sensor is used to measure piston displacement, for example, when installed in a wave-compensation hydraulic actuator.
B. Product Features of the SCHWERLL Servo Hydraulic Cylinder:
- In applications involving high-speed motion, high-speed servo hydraulic cylinders must be used; for example, when the piston rod displacement speed reaches 10 m/s, 15 m/s, or 20 m/s, a high-speed servo hydraulic cylinder is required.
- When a high-speed servo hydraulic cylinder is equipped with a precision piston displacement sensor, closed-loop control of the system can be achieved. By accurately measuring the piston rod’s displacement in real time, closed-loop regulation of the system’s flow rate, velocity, and acceleration becomes possible.
