As the industrial environment continues to press forward with the Industrial Internet of Things (IIoT), also known as Industry 4.0, there is one mechanical technology product that has joined the ranks of smart connected devices. The fluid power industry is embracing the world of Industry 4.0 by using smart sensors, which allow hydraulic systems to provide the health status of electrohydraulic machines. In addition, data analytics introduces predictive maintenance practices that allow OEM manufacturers to review system concerns before they can manifest into serve shutdown scenarios.
Shown is a line of wire sensor integrated with a hydraulic cylinder. (Image source: SIKO)
Fluid power is a technology that uses pressurized oil to create mechanical movement. Components such as cylinders, motors, and directional control valves allow this pressurized oil to provide the required forces needed for mechanical movement. The trend to include electronics and hydraulics has intensified with the Industry 4.0 digital factory vision of original equipment manufacturers. As electromechanical systems are improved with the aid of electronics and sensors, hydraulics is using these intelligence-based components for energy efficiency and precision control.
The benefits of adding smart sensors to hydraulic systems include data collection of the health status of fluid power components—machine to machine communications that supports the IIoT or Industry 4.0 smart factories initiatives. Inventory management of hydraulic components can be accomplished using radio frequency identification (RFID) based sensors attached to directional control valves, manifolds, or check valves. With the use of electromagnetic fields, identification tags attached to hydraulic components can aid in streamlining the inventory of such fluid power devices. Also, smart sensor integration with hydraulic components provides a holistic system architecture, which allows adaptability to the interdisciplinary field of mechatronics.
Hydraulic pressure and components can be monitored and inventoried using RFID sensor technology. (Image source: Bestech)
There are a variety of smart sensors for monitoring the mechanical movement of hydraulic components within a fluid power system. Position sensing switches are commonly used to detect cylinder end of stroke motion. To decelerate the cylinder, the position sensing switch detects the end of stroke using a reed or proximity detection device.
These devices are non-contact sensing components. Their operation depends on the disturbance of a magnetic field. With proper signal conditioning, that magnetic field will act as a switch for decelerating the cylinders' extend or retract position. Hall effect switches are another method of detecting the presence of magnetic flux. Upon detection, the small, three pin, solid state device will provide a digital signal that can easily be read by a programmable logic controller (PLC).
The PLC will then control the hydraulics solenoid-controlled check valve, thus restricting fluid flow to the cylinder. For monitoring the rotational motion of a hydraulic motor actuator, rotary encoders are commonly used. The position of the hydraulic motor actuator is determined by the number of digital pulses produced by the encoder or counting disc. This series of digital pulses is sent to the PLC for positional information and control of the hydraulic motor actuator.
The industrial implementation of smart sensors in hydraulics ranges from mobile equipment systems to subsea applications. Lift buckets require proper leveling to ensure safety of the maintenance technician working several hundred feet in the air. Therefore, these specialized mobile equipment systems require linear transducers for proper operation of the hydraulic cylinders, providing positional feedback data to the human machine operator unit.
Monitoring the attitude or height of the extended hydraulic cylinder is dependent on inclinometer or tilt sensors for such distance angle measurement devices. The use of gyro-based sensors using microelectromechanical systems (MEMS) provides angle positional data from the inclinometer. As with all smart sensors used with hydraulics, the sensing components along with the electronics are encapsulated and hermetically protected in a stainless-steel housing.
In addition, smart sensors are allowing the vital health status data of hydraulic components and systems to be obtained easily with wireless communications. Bluetooth Low Energy (BLE) technology deployed in mobile devices allows data collection from embedded smart sensors to obtain temperature, pressure, and vibration data wirelessly. The performance of a hydraulic valve can be optimized and tuned using this low power communication technology aided by smart sensor technologies. Additional information on smart sensors and IoT technologies can be obtained from Deloitte Insight’s website.
Rotary encoders can determine the position of hydraulic motor actuators using a digital disc. (Image source: Leine and Linde)
The PTK29 Positilit inclination can measure ±180° tilt angle in one axis of lift motion. (Image source: ASM Sensors)
Don Wilcher is a passionate teacher of electronics technology and an electrical engineer with 26 years of industrial experience. He’s worked on industrial robotics systems, automotive electronic modules/systems, and embedded wireless controls for small consumer appliances. He’s also a book author, writing DIY project books on electronics and robotics technologies.