MTS Magnetostrictive
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Model RH Rod-style position sensor Model RP Profile-style position sensor Temposonics ® Magnetostrictive, Absolute, Non-contact Linear-Position Sensors Intelligent Hydraulic Cylinders Improve Off-Road Equipment White Paper SENSO RS ® Document Part Number 551300 Revision A By Hub vom Berg, Technical Marketing Manager of MTS Sensors THE NEED FOR SAFETY REQUIREMENTS The rapid advances in Electronic Control Units (ECU) and sensors al- low for new functionality and more safety features being implemented in mobile hydraulic systems. From GPS-controlled steering, blade control, and comfort features on agricultural machines to steer-by- wire, bucket position control and more on construction machinery, these advances enable highly developed features to be implemented upon the customer’s request. Initiated by the European Union (EU) and commonly implemented in other countries and the USA (new regulations in North Carolina), the new functionality is also used to improve the safety of equipment where human lives are on the line. The most recent crane collapse during repair efforts on the National Cathedral in Washington, DC after the East Coast earth quake is a current example that illustrates the need for more safety features on equipment. INTELLIGENT HYDRAULIC CYLINDERS Intelligent hydraulic cylinders are key components of these features and they are used to determine the position of the crane arm and the outriggers. By knowing the absolute extension of the cylinders, this allows the ECU to determine the safe foundation of the complete rig through knowing the position of the outriggers and the extension and angle of the boom. Although there are a variety of technologies such as resistive technology, Hall-effect technology, LVDT’s and rotary encoders on the market, the best technology today is magnetostrictive linear position sensing technology inside the cylinder. The advantages of this technology include: • In-cylinder protection (protected from mechanical damage) • Non-contact features (no wear on the sensor) • High shock and vibration rating • 200 V/m EMI resistance • High resolution, very stable output • Safety rated to EN 61508 SIL-2 rated • Performance to EN 13849-1 Level D The position of the magnet is determined with high precision and speed by accurately measuring the elapsed time between the start of the interrogation pulse and the arrival of the resulting strain pulse. The measurement is absolute and does not require recalibration or zeroing after a power loss. The non-contact feature between the sensor and the magnet eliminates wear and guarantees durability and repeatability. Fig. 1 - Mobile Crane
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Transcript of MTS Magnetostrictive
Model RH Rod-style position sensorModel RP Profile-style position sensor
Temposonics®
Magnetostrictive, Absolute, Non-contact
Linear-Position Sensors
Intelligent Hydraulic Cylinders Improve Off-Road Equipment White Paper
SENSORS
®
Document Part Number 551300 Revision A
By Hub vom Berg, Technical Marketing Manager of MTS Sensors
THE NEED FOR SAFETY REQUIREMENTS
The rapid advances in Electronic Control Units (ECU) and sensors al-low for new functionality and more safety features being implemented in mobile hydraulic systems. From GPS-controlled steering, blade control, and comfort features on agricultural machines to steer-by-wire, bucket position control and more on construction machinery, these advances enable highly developed features to be implemented upon the customer’s request.
Initiated by the European Union (EU) and commonly implemented in other countries and the USA (new regulations in North Carolina), the new functionality is also used to improve the safety of equipment where human lives are on the line. The most recent crane collapse during repair efforts on the National Cathedral in Washington, DC after the East Coast earth quake is a current example that illustrates the need for more safety features on equipment.
INTELLIGENT HYDRAULIC CYLINDERS
Intelligent hydraulic cylinders are key components of these features and they are used to determine the position of the crane arm and the outriggers. By knowing the absolute extension of the cylinders, this allows the ECU to determine the safe foundation of the complete rig through knowing the position of the outriggers and the extension and angle of the boom.
Although there are a variety of technologies such as resistive technology, Hall-effect technology, LVDT’s and rotary encoders on the market, the best technology today is magnetostrictive linear position sensing technology inside the cylinder.
The advantages of this technology include:
• In-cylinder protection (protected from mechanical damage)
• Non-contact features (no wear on the sensor)
• High shock and vibration rating
• 200 V/m EMI resistance
• High resolution, very stable output
• Safety rated to EN 61508 SIL-2 rated
• Performance to EN 13849-1 Level D
The position of the magnet is determined with high precision and speed by accurately measuring the elapsed time between the start of the interrogation pulse and the arrival of the resulting strain pulse. The measurement is absolute and does not require recalibration or zeroing after a power loss. The non-contact feature between the sensor and the magnet eliminates wear and guarantees durability and repeatability.
Fig. 1 - Mobile Crane
Temposonics® Linear-Position Sensors - White PaperIntelligent Cylinders White Paper, Document Part No.: 551300, Revision A 02-12 MTS Sensors
Since the sensor is integrated in the hydraulic cylinder the overall protection is high. Using a proprietary M12x1 connector system for the electrical output, in addition, guarantees IP69k protection against the environment as well as protection against physical damage to the sensor and the wires.
Fig. 3 - Detail of the M12x1 Connector System
MTS Sensors has developed safety rated sensors with analog and CANOpen outputs to satisfy all applications in the crane, man-lift, drilling and related equipment markets.
The proven Model MH package allows for easy integration into the cylinder and the standard length of 2” (50mm) to 100” (2,500mm) covers most of the applications. The accomplished SIL-2 rating according to EN 61508 satisfies all regulations for mobile hydraulic markets including construction, agricultural, above ground mining and material handling hydraulic cylinders.
HOW MAGNETOSTRICTION WORKS
Magnetostriction is a term that describes the tendency of some materials to change shape, constrict or elongate in the presence of a magnetic field. Normally, a material’s magnetic domains are randomly oriented. If a magnetic field is applied, those domains will align, caus-ing a change in shape or length.
A magnetostrictive position sensor takes advantage of this effect by inducing a mechanical wave or strain pulse (as shown below) in a specially-designed magnetostrictive wire called a waveguide. The time of flight of this pulse is measured and can be equated to distance be-cause the speed of traverse is very constant and repeatable. The pulse is created by momentarily causing the interaction of two magnetic fields.
Fig. 4 - Magnetostrictive Technology Diagram
One magnetic field originates from a permanent magnet, which passes along the outside of the sensor tube. The other electromag-netic field, encompassing the entire length of the waveguide, is created when a current interrogation pulse is applied to the wave-guide.
At the interaction point between these two magnetic fields a torsional strain pulse is produced, that travels at the speed of sound in the spe-cialized waveguide alloy (about 3.55 microseconds per centimeter of travel) along the waveguide path until the pulse’s arrival is detected at the head or mode converter end of the sensor.
The position of the magnet is determined precisely by measuring the elapsed time between the creation of the current pulse and the arrival of the strain pulse. That information is converted either to a duty cycle derived analog signal or is read as a serial or bus signal by the user’s controller. As a result, accurate non-contacting position sensing is achieved with absolutely no wear to any of the sensing elements. The strain pulse is small, on the order of 20 to 30 microstrain, resulting in virtually no fatigue of the waveguide.
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Fig. 2 - Model MH Sensor in Cylinder Cutaway
SENSORS
®
MTS and Level Plus are registered trademarks of MTS Systems Corporation.All other trademarks are the property of their respective owners.
Printed in USA. Copyright © 2011 MTS Systems Corporation. All Rights Reserved in all media.
Document Part Number: 551300, Revision A 02/12
MTS Systems CorporationSensors Division
3001 Sheldon DriveCary, North Carolina27513, USATel.: +1-800-633-7609Fax: +1-919-677-2343 +1-800-498-4442e-mail: [email protected]://www.mtssensors.com
MTS Sensor TechnologieGmbH & Co. KG
Auf dem Schüffel 9D - 58513 Lüdenscheid, GermanyTel.: +49-2351-9587-0Fax: +49-2351-56491e-mail: [email protected]://www.mtssensor.de
MTS Sensors TechnologyCorporation
737 Aihara-cho, Machida-shiTokyo 194-0211, JapanTel.: +81-42-775-3838Fax: +81-42-775-5516e-mail: [email protected]://www.mtssensor.co.jp
ABOUT MTS SENSORS:
MTS Sensors, a division of MTS Systems Corp., is the global leader in the development and production of magnetostrictive linear-position and liquid-level sensors.
MTS Sensors Division is continually developing new ways to apply Temposonics® magnetostrictive sensing technology to solve critical applications in a variety of markets worldwide. With facilities in the U.S., Germany, Japan, and China, MTS Sensors Division is an ISO 9001 certified supplier committed to providing customers with innova-tive sensing products that deliver reliable position sensing solutions.
