This content is excerpted from Sensor Technology Alert and Newsletter, a sensor intelligence service published by the Technical Insights unit of Frost & Sullivan.
Radio frequency (RF) transmission is a vital element in wireless sensing and control solutions, which are poised to impact diverse applications, such building control, industrial automation/machine preventive maintenance, security/defense, test and measurement, and environmental monitoring. While the infrastructure or protocol for communicating sensor data wirelessly is important for establishing standards for wireless transmission, advances in radio transmission technology are also critical for achieving more reliable and efficient wireless sensing solutions.
As wireless sensors become more established and begin to proliferate in real-world applications, it will become increasingly important to achieve battery-less wireless sensing solutions. Such systems would not require significant maintenance, would not engender the potentially onerous problem of disposing of large quantities of batteries, and would consume a minute amount of energy.
EnOcean GmbH, founded in 2001 as a spin-off of Siemens AG, is finding opportunities in varied application areas (such as building automation control, automotive tire pressure monitoring, industrial automation, logistics, emissions testing) for their battery-less radio transmission technology, originally developed at Siemens' central research laboratory. EnOcean's transmitter modules (which contain a sensor or an interface to a sensor) are capable of scavenging minute amounts of energy from the environment. The changes in energy entropy are due to a detectable event, such as a change in, for example, temperature, vibration, pressure, light, or motion. The energy harvested is used to transmit very short-duration, very low energy consuming radio signals containing data collected by the sensor. In addition to being ecologically friendly, the technology purportedly less electromagnetic pollution, since it generates electromagnetic fields that are significantly lower than that of conventional electrical installations.
EnOcean's battery-less transmitters (and radio switches and sensors) transmit information based on the company's radio protocol in the license-free 868.3 MHz band. Each transmitter receives a unique 32-bit address when it is manufactured. Such transmitters have an operation range of up to 300 meters.
In EnOcean's PTM 100 piezo radio transmitter module, power is supplied by a built-in piezo power generator. A piezo energy transducer is activated by a bow, which can be pushed by an appropriate pushbutton or switch rocker. When the energy bow is pushed down, electrical energy is created and an RF telegram is transmitted, including a 32-bit module IP ID. Releasing the energy bow generates different telegram data, therefore, every telegram contains information indicating that the bow was pressed or released.
Armin Anders, Product Marketing Manager, explained that EnOcean's battery-less transmission solutions are, at present, primarily used in building automation applications, as well as in such applications as, for example, industrial automation (radio switches for manufacturing assembly lines, robots, monitoring wheel axis temperature for preventive maintenance) and exhaust gas emissions testing. Moreover, EnOcean is finding key opportunities for its battery-less radio technology in automotive tire pressure and temperature monitoring systems.
EnOcean has thus far sold about 50,000 radio nodes (consisting of a transmitter and sensor) for building automation or building engineering. In addressing the building automation segment, EnOcean partners with such companies as PEHA, WAGO, Siemens, OSRAM, Balluff, steute, ThermokonSensortechnik (for sensor technology), Wieland, Omnio, Beckhoff, Schlapps & Partner, W&T, Servodan, and MSR Electronic.
To exploit opportunities in automobile tire pressure monitoring (which is poised to become a very significant unit-volume market, driven by legislation), EnOcean is partnering with a European-based tire pressure monitoring system (TPMS supplier to develop a battery-less transmitter that would mounted in the wheel rim of each tire along with a silicon pressure sensor. A piezo element, mounted near the sensor and transmitter module, would bend and create energy, activated by wheel vibration.
In such a battery-less TPMS, a transmitter or transponder mounted in each wheel rim would send data from the air pressure and temperature sensor to a central receiver or transceiver. A battery-less TPMS eliminates certain issues associated with batteries, such as limited life span, the potential for impaired performance when subjected to temperature conditions experienced by automotive components, and the possibility that the weight of the battery could distort the tire's shape at high speed, resulting in a loss of air pressure.
Anders pointed out that there are some technical challenges in achieving the battery-less TPMS that will use EnOcean's transmission technology. For example, different forces affecting the wheel (such as centrifugal force) must be identified in order to successfully harvest the energy from wheel vibration. The battery-less TPMS must be able to work effectively at low speeds and high speeds; and the radio must have a very fast transmission rate. Sensors used in conjunction with EnOcean's radio in such a battery-less TPMS would need to be able to operate on very low power (about 1 milliamp) and to be able to turn on and off very rapidly (in about one millisecond). Tire pressure monitoring systems equipped with EnOcean's battery-less transmission technology are expected to appear in mass-produced vehicles around 2007 or 2008.
In the U.S., opportunities for direct tire pressure monitoring systems are being fueled by the Transportation Recall Enhancement, Accountability, and Documentation (TREAD) Act of November 2000, which empowered the U.S. National Highway Traffic Safety Administration (NHTSA) to improve vehicle safety initiatives, including the installation of warning systems on new sold in the U.S. to indicate when tires are significantly under-inflated.
NHTSA' original ruling essentially allowed for two alternatives for TPMS on light vehicles for the sale in the U.S.: the TPMS must warn the driver when tire pressure is 25% or more below the placard pressure for on to four tires; or the TPMS must warn the driver when tire pressure is 30% or more below the placard pressure for any single tire. The original ruling allowed for using either the direct TPMS( where a tire pressure sensor is mounted in each wheel), or the indirect TPMS (which determines tire inflation pressure by measuring relative rotational differences in the wheels). The indirect system, which is designed for use with the anti-lock brake system, cannot determine when all four tires lose air at about the same rate.
NHTSA had to revise its original ruling, following a court ruling that found that only the first alternative was reasonable. Circa autumn 2004, NHTSA, NHTSA published a new notice of a proposed rulemaking (NRPM) that would require: a four-tire TPMS capable of detecting when a tire is more than 25% under-inflated and of warning the driver at that time; a warning light to illuminate and stay on until all tires that are more than 25% under-inflated have been re-inflated; a TPMS malfunction indicactor to warn drivers when the TPMS is not working properly; and a bulb check to be conducted at vehicle ignition.
Compliance with respect to the proposed rules would begin with light vehicles manufactured on or after September 1, 2005 (MY 2006) under a three-year phase-in period. The NRPM calls for 50% of all passenger cars and light trucks vehicles manufactured in model year 2006 (September 1, 2005-August 31, 206) to be equipped with an approved TPM system; 90% of such vehicles manufactured in model year 2007 (September 1, 2006-August 31, 2007) to be equipped with an approved TPM system; and 100% of such vehicles manufactured after September 1, 2007 to be equipped with an approved TPM system. As of early March, NHTSA had not yet finalized the rulemaking. Knowledgeable sources have told Sensor Technology that NHTSA may reduce the portion of light vehicles made in MY 2006 that would be required to have a TMPS.
The Wireless Sensors in Building Automation report, from the Technical Insights Div. of Frost & Sullivan (published February 2005), analyzes such applications as structural health, HVAC, security, fire and safety, and lighting control. The report on "Advances and Trends in Wireless Technologies," from the Technical Insights Div. of Frost & Sullivan (published June 2004) includes an assessment of radio frequency and optical communication technologies.
Details: Armin Anders, Product Marketing Manager, EnOcean GmbH, D-82041 Oberhaching, Kolpinging 18a Germany. Phone: +49-89-6734-6890. E-mail: [email protected]