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Intelligent Fastening for Automotive Electronics
December 31, 1969 |Estimated reading time: 9 minutes
Automotive OEMs and suppliers share a drive to enhance assembly efficiency and productivity, reduce time-to-market, produce higher-quality products at competitive prices, and meet regulatory standards for mileage, safety and the environment. The industry also must meet demand for increased vehicle performance, comfort, convenience, communications and security.
By Seshu Seshasai
Content and complexity of automotive semiconductor technology for various uses continue to grow. Allied Business Intelligence predicts that the worldwide automotive semiconductor market will expand to more than $17 billion annually by 2007, up from $12.3 billion last year. Strategy Analytics reports that electronic systems will grow to more than 30 percent of typical car cost, vs. today's 20 percent.
Intelligent fastening removes the physical link between the tool and fastener. Designed with actuating mechanisms, intelligent fasteners feature embedded microchips that control the fastening process through digital instructions from a remote tool.
Fasteners typically account for only 5 percent of vehicle production costs. Yet using fasteners in assembly systems can reach 40 percent of production overhead. Intelligent fastening potentially can reduce these costs through a new approach to automobile production and service.
- Design. Designers can focus on performance requirements of products, subassemblies and component parts rather than assembly. Joints can be shifted away from high-force transfer areas, allowing different fastening options. This new capability could help marry form to function.
- Assembly. Subassemblies in conventionally manufactured products include arrays of fasteners that dictate sequencing requirements of production, maintenance and service procedures. With intelligent fasteners integrated within components, a network of intelligent fasteners could be remotely activated by electronic commands.
- Service. Microchips embedded in fasteners respond only to encrypted signals, restricting access to service procedures. These procedures would be stored in fastener control software, ensuring installation of authorized replacement parts. A central database would retain information on fastener status and maintenance history. All data would be accessible instantly to document warranty claims.
Original parts with unique, electronically controlled serial numbers could be authenticated from the central database prior to assembly. Software also could manage inventory through a central database, as well as provide service manuals for access by technicians.
- Sensing. Integrated sensors within intelligent fasteners could be programmed to detect, analyze and report urgent problems. As telematics progress, fastener information could be transmitted in real time to service centers, documenting product performance, status, wear and tear, and maintenance procedures. Embedded sensors could signal impending performance failure of critical parts or assemblies based on wear parameters.
- Recycling. Intelligent fastening could help simplify disassembly of complex products using software commands to separate parts for disposal or reuse. More efficient recycling at the end of automobile life cycles also could reduce overall production costs.
- Customization. Intelligent fasteners could allow easy part change-out in aftermarket customization while giving OEMs greater control of genuine parts.
With intelligent fasteners, means of actuation is integrated into the fastener itself. Otherwise, they can be engineered to meet the same application requirements of load, durability and serviceability as conventional fasteners. They can be either pins or strips that are mono-stable (defaulting to a locked state) or bi-stable (requiring actuation to lock or unlock).
Intelligent fasteners use actuators, which typically use smart materials to drive the fastening mechanism. Among these are shape memory alloys or polymers that change shape to a predetermined form under the external influence of electricity, heat and magnetic fields. Upon receiving a command from a remote tool, the microchip electrically activates the smart material actuator, which heats to a prescribed temperature, changing shape and driving the fastening mechanism (Figure 1). At the end of the control cycle, energy is removed and the fastener reverts to its original position.
Figure 1. Upon receiving a command from a remote tool, a microchip electrically activates a smart material actuator, which heats to a prescribed temperature, changing shape and driving the fastening mechanism. At the end of the control cycle, energy is removed and the fastener reverts to its original position.
Embedded electronics include a control device, sensors and the intelligent processor. The control device switches energy to the actuating mechanism, and also can provide secondary switching functions for fastened components. For example, an intelligent fastener could secure a vehicle wing mirror and also control its adjustment.
Depending on fastener design, sensors could track such parameters as internal conditions, fastener stress levels and whether the fastener is engaged. In assembly processors, sensors could track the relative position between parts and other feedback on the attachment of components and subassemblies.
Figure 2. A remote, wireless device sends instructions to intelligent fasteners through a software application program controlled by a human operator.
The intelligent processor controls all fasteners and associated activity. These include activating energy switches, receiving information from sensors, and communicating with the network to which it is attached. The processor can be configured to provide multiple levels of redundancy for product reliability.
Fastener Operating System
Proprietary electronics embedded in intelligent fasteners are controlled by an operating system consisting of real-time executive input/output (I/O) drivers. An applications programming interface provides a connection between the intelligent fastener and application software.
The operating system controls fastener functions including switching energy to the fastener actuating mechanism, linking the intelligent fastener to surrounding data networks, and reporting fastener status. Connection to a network allows storage and capture of information about fastener status while maintaining a historical record.
When multiple fasteners secure an assembly, typically only one fastener would carry an embedded microchip. This "master" fastener activates or deactivates multiple "slave" fasteners that release simultaneously to connect or remove complex parts quickly. The operating system can support up to 16 I/O channels for control of multiple slave fasteners, external devices and sensors.
Figure 3. Airbags are exposed at the surface of the housing, allowing quick and easy removal. Intelligent fasteners concealed in the housing deny access to unauthorized personnel, restricting removal to authorized technicians using proprietary codes transmitted remotely to the fasteners.
The master fastener also can run diagnostics such as checking stress levels, load status, and ambient temperature and environmental conditions of each fastener under its command. Information is gathered in real time and communicated over a data bus to personnel.
The operating system also can perform these functions:
- Communications and networking. These support a range of interfaces and protocols, allowing networks of fasteners to communicate with each other and to external services, networks and remote activation software.
- Energy optimization. This software algorithm includes routines to optimize activation of various fastener mechanisms, as well as reduce power consumption and physical demands on actuators.
- Ancillary switching logic. The operating system can control ancillary switching functions related to actual fastening applications.
System Architecture
Standard programming tools enable users to develop software applications to program an assembly sequence and add functionality to embedded intelligent fasteners. System architecture allows the technology to be integrated into different types of networked environments over multiple network protocols and hardware interfaces. The architecture consists of four principal elements.
- Master control database. This is the central data repository for unique fastener identification information. Storage facilities include status history and authentication and authorization of control information.
- Intelligent tool. This remote, wireless device sends instructions to intelligent fasteners via a software application program controlled by a human operator or automated assembly or service system (Figure 2). Intelligent tools in the field can automatically download algorithms for control of new fastener types.
- Communications concentrator. This device supports onboard networking and links to the intelligent tool, providing the interface between the control system and the intelligent fastener network. The communications concentrator can support multiple industry standard networks, such as a controlled area network (CAN) bus or Bluetooth.
Integration into Automobiles
- Wire harnesses. Harnesses are moving from traditional relay circuit methods of vehicle component control towards a networked system of smart, multiplexed silicon switching. For example, traditional car doors contain about 80 wires within the door wiring harness, controlling functions such as the rear vision mirror, door locks, window motors and in-door courtesy lamps. By comparison, today's cars use multiplex modules within the doors. These are connected to the vehicle computer body control module via a CAN bus, which can reduce wire content by 50 percent.Intelligent fasteners could attach the internal lining to the car door, and also control the door lock and the window motor. The vehicle computer would transmit instructions between the intelligent fastener and the remote tool and be connected by the CAN bus network. The fasteners would reside directly on the CAN bus or in a sub-network, typically a local interconnected network (LIN) that controls door component functions. This sub-network comprises a communication gateway attached to the CAN backbone. The multiplex module controls the network of components beneath it, including the door lock and the window motor.
- Airbags. Today's airbags are exposed at the surface of the housing, so it only takes a couple of minutes to remove them. More than 50,000 are stolen every year in the U.S. alone. Airbags also are cumbersome to install, requiring stops at assembly stations to screw them into place. Service can be carried out by anyone with the right tools, but with no automated log (Figure 3).Intelligent fasteners can be concealed in the airbag housing. That means there are only two ways to remove them: by authorized codes transmitted remotely to the fasteners, or by destroying the housing and airbag, rendering them useless. Only genuine replacement parts could be installed, and each service process would be logged and stored for future reference.
- Headlamps. Headlamps consist of a complex arrangement of snap clips and mechanical fasteners on an adjustable sub-assembly. By using intelligent fasteners, the lens and lamp assembly would be remotely released from the sub-assembly, greatly reducing time and cost to install, service and replace parts. Removing the need for rear access screws also would allow space savings.
- Roof racks. With the press of a button car owners could remove roof racks and other accessories to reduce wind noise, drag and vehicle weight.
- Spare tires. Intelligent fasteners would release the spare tire with a point-and-click button affixed to a key chain or from the instrument panel.
- Radios and stereos. By replacing clips and concealed screws with intelligent fasteners, installing and replacing entertainment systems becomes as simple as pressing a remote control button.
- Interior trim. Intelligent fasteners expedite assembly through simultaneous or sequenced release of a networked fastening system.
- Seatbelts. Wireless or satellite signals from emergency control centers could release seatbelts, infant restraints and seating systems, enabling instant release of trapped or injured passengers from their cars in emergency situations.
- Black boxes. Intelligent fastening would provide authorized access to black boxes, preventing tampering or removal of the circuit board or connector during servicing.
Conclusion
Intelligent fastening has the potential to advance the speed, flexibility, flow and cost savings automotive OEMs and suppliers seek. The global automotive community now has a new capability to design for assembly and disassembly, as well as security and safety, by integrating the mechanics of fastening processes into components.
Seshu Seshasai, Ph.D., executive vice president, Textron Fastening Systems, may be contacted at sseshasai@tfs.textron.com.