Position-sensing hydraulic cylinder

A position-sensing hydraulic cylinder is a hydraulic cylinder with an integrated position feedback sensor to determine its current position.

Position-sensing hydraulic cylinders may be found in heavy industry, subsea, and mobile equipment applications.^[1]

Linear Displacement Transducers[edit]

Internal LDT[edit]

With In-cylinder Linear Displacement Transducers (LDTs), the hydraulic cylinder’s piston rod must be bored through its center to accommodate certain elements of the LDT — usually the waveguide tube of a magnetostrictive transducer.^[2] The machining and additional production steps associated with “gun drilling” the piston rod can add cost to the finished cylinder. Magnetostrictive LDTs provide extremely high accuracy, down to one micron.^[3]

Hydraulic cylinder with a Hall effect sensor mounted along its barrel to sense position of a magnetic piston inside. The sensor is mounted without having to gun drill the piston rod, yet its size and location protect it from potential environmental damage.

External LDT[edit]

External linear displacement transducers (LDTs) eliminate the need for a hollow hydraulic cylinder rod. Instead, an external sensing “bar” utilizing Hall-Effect technology senses the position of the hydraulic cylinder piston. This is accomplished by the placement of a permanent magnet within the piston.^[4]

An external Linear Displacement Transducer (LDT) utilizes a magnet that generates a magnetic field, which passes through the steel wall of a hydraulic cylinder. This magnetic field provides a locating signal to an external sensor.

Advantages of external LDTs include:

Preservation of Rod Strength: The full buckling strength of the rod is maintained.
Ease of Maintenance: The cylinder design simplifies assembly, installation, and servicing.
Versatility in Connectivity: There is a wide range of sensor inputs and outputs available.
Accessibility: The external sensor is easily accessible and can be replaced if necessary without the need for recalibration.
Durability: The small sensing bar is positioned along the exterior of the hydraulic cylinder, reducing the risk of environmental damage.
Accuracy: The positioning accuracy is +/- 0.5 mm, which is sufficient for most mobile equipment applications.

References[edit]

^ Herceg, Edward. "Position Sensor Technology Comparison for Hydraulic Cylinder Feedback" (PDF). Archived (PDF) from the original on 2024-04-25. Retrieved 2024-04-25.
^ Hydraulics & Pneumatics Magazine Archived 2011-07-18 at the Wayback Machine
^ Journal, Fluid Power (2019-01-10). "Strong, Tough, and Reliable: Linear Displacement Transducers Take on the Most-Demanding Applications". Fluid Power Journal. Retrieved 2024-04-25.
^ "Electronic Position-Sensing Hydraulic Cylinders.(Energy Manufacturing Company Inc introduces cylinders having electronic position-sensing option)(Brief article) - Design News - HighBeam Research". 2012-10-23. Archived from the original on 2012-10-23. Retrieved 2023-12-09.

External links[edit]

[1] Herceg, Edward. "Position Sensor Technology Comparison for Hydraulic Cylinder Feedback" (PDF). Archived (PDF) from the original on 2024-04-25. Retrieved 2024-04-25.

[2] Hydraulics & Pneumatics Magazine Archived 2011-07-18 at the Wayback Machine

[3] Journal, Fluid Power (2019-01-10). "Strong, Tough, and Reliable: Linear Displacement Transducers Take on the Most-Demanding Applications". Fluid Power Journal. Retrieved 2024-04-25.

[4] "Electronic Position-Sensing Hydraulic Cylinders.(Energy Manufacturing Company Inc introduces cylinders having electronic position-sensing option)(Brief article) - Design News - HighBeam Research". 2012-10-23. Archived from the original on 2012-10-23. Retrieved 2023-12-09.

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