Cutting-Edge Automotive DesignJune 8, 2007 By: Mike Donfrancesco, InterSense Inc., Dean Wormell, InterSense Inc. Sensors
While some automotive manufacturers still use clay models to prototype new cars, most of the industry's R&D centers now have the technology to create virtual environments in which to view and manipulate their designs. The use of virtual models to collaboratively review and modify designs on a desktop computer is, for the most part, a basic capability of any automotive manufacturer today, but there is one aspect of the design process—the use of interactive, 1:1 ratio immersive displays—that sets apart the cutting-edge designers from the rest of the field.
With the cost of vehicles steadily increasing as a result of heightened safety standards and growing customer demand for bells and whistles, a major overhaul of the automotive design process is taking place. Sensor technology used in interactive immersive displays is at the heart of this change, helping automakers identify, design, and assess vehicle improvements. In tandem with 3D software and other visualization technologies, motion-tracking sensors enable interactive testing and design via computer models in a fraction of the typical design time.
Interactive immersive displays are a collection of complementary technologies that, when used together, can save auto manufacturers time and money. Motion-tracking technology and advanced visualization techniques, coupled with collaborative design processes, have enabled auto manufacturers to reduce the average design time from three years to 18 months (Figure 1). The shorter design cycle provides manufacturers with faster time to market, enabling the designer to keep up with changing consumer requirements and offers the company a quicker return on its investment in new models and features.
Figure 1. Interactive, 1:1 immersive displays, which combine motion-tracking sensors, advanced visualization techniques, and 3D software, enable auto manufacturers to reduce the average design time of a new model from three years to 18 months
Bringing Auto Designs to Life
Realization of these significant cost and time savings begins at the auto manufacturers' R&D centers. Modern manufacturers have for many years been able to digitize a car model and visualize it on a desktop computer screen. However, rendering that same design in a stereoscopic format that enables you to visualize and interact with the model in an intuitive manner, while maintaining the correct visual perspective—for example, viewing the dashboard as if you were sitting inside the car, or walking around the car and correctly viewing it relative to your movement—is something new.
With two devices, a head tracker and a handheld wand (Figure 2)—which act much like the keyboard and mouse on a desktop computer—auto manufacturers can interact with the models in ways that were not previously possible. The head tracker measures your head's position so that the stereoscopic view can be updated in real time as you move within the environment (e.g., the ability to look around the headrest when sitting in the back seat), and the wand lets you fly through an environment with a joystick-like movement in a particular direction. For instance, with the wand, you can select and open a car door, zoom in on an object, then rotate it for closer inspection.
Figure 2. A motion-tracking wand (left) and head tracker (right)
Optical, magnetic, or hybrid inertial-ultrasonic motion tracking sensors may be integrated into the head tracker and handheld wand. Generally, these technologies provide <1° of accuracy in orientation and ~1 mm position accuracy. Optical motion tracking is generally viewed as a high-end solution, relative to the other technologies, and offers an easy calibration process. However, at least two cameras must have a clear line of sight to three retroreflective markers at all times. The three markers create a plane, which provides the orientation of the device; if one marker fails to be seen, you will lose orientation tracking. To minimize line of sight problems, you require a large number of markers for each device, creating redundancy. While this works, it is not particularly elegant.
Magnetic motion tracking, as the name suggests, requires a magnetic source to be placed in the environment, along with small magnetic sensors embedded into the tracking devices. The advantage is the lack of line of sight restrictions, because magnetic fields from the source will pass through objects. However, when magnetic objects are introduced into the tracking area they create noise or jitter in the tracking. These foreign objects must be mapped out within the environment to ensure acceptable tracking performance. While somewhat convenient and cost-effective, magnetic solutions are typically not wireless and have higher latency than the other technologies.
Hybrid inertial-ultrasonic sensors do not have the line of sight restrictions nor are they sensitive to the presence of magnetic objects within the tracking area. The inertial sensors— accelerometers and gyros—measure the acceleration and angular speeds of movement at rates upwards of 180 Hz. The output of the inertial sensors is fused with acoustical range measurements made by triangulating signals from multiple ultrasonic emitters placed within the room. The resulting tracking data is precise and smooth, with high sampling frequencies and a measurement latency of <3 ms. System accuracy can reach 3 mm and <1° RMS, providing the ability to detect fine movements for interaction with the virtual model.
Fast response times with low latency and little noise from the sensors are crucial to providing a realistic view of the model. The output on the visualization display must match the actual movement of the head or wand. A delay between the virtual scene and the real movement will likely cause an uncomfortable feeling, frequently called "simulator sickness."
To enhance the application and create a realistic and safe experience, sensors must be lightweight, free of wires (i.e., battery powered), and provide fast, precise measurements. Typical head trackers weigh <2 oz. and are mounted on a pair of stereo glasses worn by the user. The handheld wand sensor is designed for comfort for long working sessions, and should include the necessary buttons to interact with the model and a joystick for navigation.
Multiple locations can be linked to offer a collaborative virtual environment in which designs and data can be shared between design centers in real time. In these distributed collaborations, motion-tracking sensors and systems play a key role in providing engineers at different sites with common perspectives of the vehicle design. Wands can be used to point and highlight areas of interest across the shared virtual space, which all parties in the group can view and comment on.
Beyond Motion Tracking
Although sensor-enabled motion tracking can provide the correct viewpoint and necessary data interactivity, appropriate display systems are also needed to ensure the realism of the projected image. The correct brightness, screen configuration, and image resolution are all specific to the visualization environment and are based on the requirements of the design process.
For instance, if you are reviewing the outside of a new automobile design, a large flat display (in the range of 8 in. by 10 in.) with high resolution will provide the 1:1 scale and level of detail needed to review and properly evaluate the design. On the other hand, if the design team needs to be fully immersed in the design and the associated data to evaluate sight lines, then a six-sided virtual immersive display known as a CAVE might better meet your needs. Alternatively, should you need a more flexible system, a reconfigurable display, which can be converted to a large flat panel or box shape, may be the best choice.
The 3D data used in auto design (and, for that matter, any 3D data) can also benefit from stereoscopic viewing. Stereoscopic glasses (Figure 3) allow you to more easily determine the depth of positions within a design. Stereoscopy is important when viewing complex spatial relationships between data points (e.g., components of an engine, wiring in the interior of the car, or components of the dashboard). Coupled with the sensors in a motion-tracking system, the stereoscopic glasses provide the ability to view data more naturally, ultimately helping you identify potential conflicts in the design well before a physical prototype is developed.
Figure 3. Stereoscopic glasses allow you to view complex spatial relationships and more easily determine the depth of positions in design visualizations
Auto manufacturers must also consider the software programs used in the immersive display, as well as the graphics engines and image processors used, all of which help provide the most photo-realistic imagery for design assessments. When these programs are combined with motion-tracking sensors, you're able to review highly detailed models with intuitive, natural body motions (e.g., moving your head to look around an object), as opposed to mimicking these movements with a mouse and keyboard.
Bringing Data Together
Just as a puzzle has many interlocking pieces, an interactive, 1:1 ratio immersive display system is the combination of complementary technologies, including the right display, the correct software, stereoscopic glasses, head trackers, and handheld wands for navigation. Advanced motion-sensor technology provides you with the feeling that you're interacting with the real world.
At its core, the fast data update rates and low system latency available from motion-sensor technology ensure the images on the screen are believable. With these realistic images, provided at the right perspective through the head trackers and stereoscopic glasses, you can identify design problems and potential areas for modification. Interactive immersive displays dramatically speed up the development cycle, improve the quality of the experience, and increase cost savings by allowing you to review and modify initial components without building prototypes. Ultimately, immersive displays ensure you can make decisions regarding your models with a high level of confidence because they allow you to view your design from new angles.
Interactive, 1:1 ratio immersive displays may not be at the fingertips of every automotive design team, but the opportunity for widespread implementation of visualization technology is just around the corner. Desktop applications that use the same interactive devices are in development and will provide the much-needed middle ground for auto designers. These new systems will enable engineers to design using immersive displays on a desktop computer, but with much greater data interactivity and model manipulation. Thus, the power of sensor-enabled motion-tracking technology will spur a new era in the evolution of automotive manufacturing and design.
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