Like most mature industries, the automotive industry is highly competitive. Customers demand quality, security, and economy. Competition requires increasingly fast times to market for new designs. Combining customer and competitive demands creates a dilemma: How to design and build the best product as fast as possible.
Experience has shown that efficiencies come to mature markets in the form of advanced automation and judicious use of new technologies. The automobile industry and its supplier ecosystem use advanced engineering across many disciplines: chemistry and thermodynamics govern internal combustion; mechanical engineering governs metal fatigue and stiffness of chassis components; and tribology describes brake and tire heating. Using thermographic techniques, automotive researchers have studied engine cooling, air conditioning, and heat dissipation of high-power electronic components. Regardless of the scientific discipline, there is a common, unifying characteristic to all these systems and components — thermal energy is critical to successful manufacture and operation. Heat degrades automotive parts and enables steel, aluminium, and plastic manufacturing processes. Heat also is produced by electronic components and is an indicator of efficient operation.
Infrared in Automotive
Automotive components and systems can be tested, measured, and evaluated using a variety of data types, depending on the test subject. The most common parameters, apart from geometrical and electrical characteristics, are pressure-and temperature-related measurements, with temperature being the most widely used in manufacturing. This has led to the increase in infrared (IR) imaging and thermographic test instrumentation, as well as discreet IR temperature measurements for monitoring manufacturing equipment and testing new designs and end-product quality.
Traditionally, thermocouples are used to make discreet temperature measurements, but these point-measurement systems can neither measure without contact, nor provide a full-field thermal image that provides temperature data over time for small, often geometrically complex and moving products. Thermographic imagers with focal plane array (FPA) sensors can provide wide-area, objective temperature measurements. New design and material improvements also have significantly increased the spatial resolution, while improved calibration has improved the IR imagers’ ability to robustly and repeatedly generate objective temperatures across a wide temperature range. This article explores the latest generation of infrared detectors and how they are answering the needs of the automotive industry in particular.
It is difficult to precisely date each step in the evolution of IR imaging, but one of the most defining parameters relates to spatial resolution, often defined as the space between the centers of two pixels on the FPA, or the FPA’s pitch. Since 1998, the most sensitive IR array sensors — indium antimonide (InSb) and mercury-cadmium-telluride (MCT) detectors — have had a 30-μm pitch. Table 1 shows the progress made by IR sensor producers during the past eight years and the development of third-generation sensors with 15-μm pitch. This performance has enabled IR camera manufacturers to, through the use of optics and electronic filtering, produce IR cameras with an effective spatial resolution down to 4 μm.
Thermographic cameras are used in five broad application categories within the automotive industry: maintenance, process control, R&D, quality control, and stress analysis. Maintenance applications typically involve the evaluation of manufacturing equipment to predict possible failures in production plants - mainly on electrical facilities. It is the most active application within the automotive industry because of the relatively low performance requirements for the IR cameras, often supported by uncooled, low-cost microbolometer- or ferroelectric-based (IR) cameras. Preventive or predictive maintenance applications are performed by maintenance technicians, which means that the cameras need to be easy to use, handheld, and can operate for extended periods on a battery for portability (see Figure 1).