Industrial automation without wires

Nov. 22, 2001
Bluetooth technology enables wireless control and sensing.

Sandy Harper
Senior R&D Project Engineer
Parker Hannifin Corp.
Irvine, Calif.

Edited by Ken Korane

Parker's Bluetooth demonstrator highlights wireless capabilities. With a Hewlett-Packard personal digital assistant, users can select, program, and actuate either a Moduflex pneumatic control-valve bank driving a series of cylinders, or an all-inone Smart Cylinder. The valves and smart cylinder feature built-in, battery-powered Bluetooth nodes.

Bluetooth technology is set to revolutionize business and consumer markets, enabling quick and easy data connections among a wide range of computing and telecommunications devices — without wires or cables. For the same reasons, it has the potential to change the face of industrial automation.

Bluetooth is a specification for short-range radio links between computers, printers, cell phones, and other portable equipment. Since it centers around a small, inexpensive, low-power radio chip, Bluetooth can also plug into devices such as mobile PCs, motion controllers, valve banks, and sensors. This makes it ideally suited for industrial monitoring and control.

Wireless advantages
The most obvious benefit of Bluetooth in industrial automation is to eliminate control cabling and significantly lower system costs. Because high-volume business and consumer applications are driving the technology, experts predict mass-produced Bluetooth chips will soon be available for around $5. Industrial-automation companies stand to benefit from economical components because even if installed costs — including microprocessor, circuitry, programming, and related hardware — are in the $40 range, a Bluetooth design will still be more economical than many of today's wired systems.

Eliminating control wiring and electrical connectors also speeds installation and reduces maintenance and troubleshooting headaches. Even a simple pneumatic system — a bank of solenoid valves driving an array of cylinders, typically fitted with two position-feedback sensors per cylinder — can mean dozens of wires running to a PLC or controller, along with air and power lines. Such complexity makes diagnosing a loose wire difficult and time consuming.

A fieldbus serial interface is a simpler solution than discrete wiring, but Bluetooth still eliminates bus cables and sensor wires. Bluetooth also offers other advantages such as built-in diagnostics and autoconfiguration capabilities not found in some serial interfaces. Developers are investigating options that will link Bluetooth wireless subsystems to existing serialinterface systems. These include embedding Bluetooth nodes into serial-interface chip sets or developing a software gateway between Bluetooth and the serial-interface microcontroller.

Bluetooth will also enable designs that are just not practical today, such as monitoring the health of machines. Wireless systems are ideal for condition monitoring for several reasons. Fitting equipment with strain gages or pressure or temperature sensors is usually too expensive with wired connections. Wires can also restrict machine movements in dynamic applications or attract unwanted contaminants in food processing and pharmaceutical applications. Aerospace manufacturers, in particular, are now investigating wireless diagnostics on aircraft systems because of the potential benefits offered by lightweight sensing and remote access.

For instance, hydraulic and pneumatic filters should be checked regularly and serviced periodically to ensure optimum system cleanliness. But when inaccessible, odds are they won't get regular inspections. Today it is possible to run RS-232 wired connections between controller and filter to monitor status but, again, this may not be feasible or economical. A Bluetooth node in the filter would eliminate the need for wires and enable remote system monitoring with a pocket PC or other handheld device.

Remote control is another option. Motion and control devices with integrated Bluetooth technology can be remotely programmed and actuated, and automatically report their status back to central controllers, handheld devices, and even cell phones.

As an example, preprogrammed motion profiles can be downloaded into an intelligent valve bank and run specific machine operations. This lets small, distributed-control systems be strategically located throughout a plant, along with the flexibility to move them as necessary. In fact, when actuation, sensing, or control is only needed on occasion, battery power can eliminate all wires to a unit.

Bluetooth also makes practical remote control in certain mobileequipment applications. Take a wireless handheld appliance, for example, that controls hydraulic cylinders on a tractor-trailer. A person with the Palm-like device could adjust trailer height as the truck backs into a loading dock.

Addressing concerns
Bluetooth is intended to be a secure connection. It provides three levels of security, from fully open and accessible to locked and password protected. Most industrial devices, such as electric motors and starters, will not interfere with Bluetooth transmissions. However, devices that emit in the 2.4-GHz range, such as microwave ovens, may require shielding.

Bluetooth also uses spread-spectrum frequency hopping. Once a connection is established, the master sets up random frequency hopping that changes transmission frequency up to 1,600 times/sec. Interference at one frequency does not impede data flow because the transmission quickly moves to another frequency.

System developers may also consider other wireless technologies such as IEEE 802.11b. This standard features faster data transmission at a longer range than Bluetooth, but it does not automatically recognize a large array of compatible devices, uses a slower, less-secure frequency hopping scheme, requires more power, and is more expensive. The intent of Bluetooth developers has always been to maintain compatibility with 802.11b. The dominant 802.11b product, WiFi or Wide Fidelity wireless Ethernet, is designed to replace cabled Ethernet connections in office or factory-control applications. Compatible Bluetooth wireless devices on the same system will facilitate distributed local-area communication that is low power, low cost, more secure, and custom configurable.

One other key issue as Bluetooth evolves is interoperability, ensuring devices from different manufacturers work together seamlessly when combined in a system. Addressing this issue is the Bluetooth Special Interest Group (SIG), comprised of telecommunications and semiconductor leaders such as Ericsson, IBM, Intel, Lucent, Microsoft, Motorola, Nokia, Toshiba, and 3Com, as well as more than 2,000 adopter/associate member companies.

The SIG has developed a test and qualification program to ensure devices are manufactured to technical specifications, and are compatible. For industrial-automation manufacturers, the availability of prequalified components such as integrated circuits makes it easier to qualify the end product or system.

Within the SIG are many application-specific working groups. Parker Hannifin, for instance, is currently participating in the Industrial Automation Study Group that will soon secure approval as a Working Group. The IA Working Group will focus on the specific interests of industrial automation Bluetooth applications, such as defining and developing profiles for industrial devices. A profile is, in essence, the method or protocol that defines data transport methods, operational performance of devices, and compatibility. Several fluid-power, motion-control, and sensor companies are members of the pending Working Group.

Parker is in the process of developing "generic" Bluetooth products that can be quickly tailored to meet a variety of requirements, as well as partnering with customers to define application-specific solutions in areas such as mobile equipment, packaging, and automated assembly. The company expects to have qualified Bluetooth products on the market within the next year.

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