Micro Inertial Navigation System. - Present Status and Development at Imego AB.

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1 Micro Inertial Navigation System - Present Status and Development at Imego AB

2 Page 1 (2) Executive Summary Imego has developed a very small prototype system for inertial navigation based on micro mechanical sensors. This micro inertial navigation system (2-INS) can navigate in conditions as difficult as 50 g accelerations and rotation speeds up to 3000 deg/s, combined with a bandwidth of at least Hz. All degrees of freedom are computed and available to the user, such as yaw, pitch and roll angles, and position. Currently our prototype hardware is a 50 mm cube and the software runs on a standby pc. This prototype is presently fully operational and collects data on site, in its native environment. A next-generation prototype is under construction and will be finished in Q4-02. The next-generation prototype will have further reduced size, weight and tracking errors. Imego has made commercially available exciting technology that, until now, has been almost exclusively found only in fighter jets and submarines. Our INS can be tailored both in shape and performance to diverse customer-specific environments. At the same time, our systems are commercially manufactured, which opens up exciting future possibilities.

3 Page 2 (3) Inertial Navigation Systems INS applications An Inertial Navigation System (INS) is a cluster of sensors which tracks the position and orientation of a body to which the cluster is rigidly attached. During the tracking, software continuously converts the sensor data into position data in stationary coordinate system that is useful to an outside observer. It is this coordinate transformation that differs a true INS from a simple collection of sensors. The sensors are accelerometers and gyroscopes and the raw sensor signals represent the acceleration and the rotational velocity of the body. The software then computes the velocity, position, orientation, and the rest of the parameters of the body. An INS produces all the information that is necessary to completely analyze and explain the motion of a car, a racket or almost any other object to which it is attached. Classically, INS is used for navigation of airplanes and submarines. The INS units for such applications are large and expensive but can navigate for a longer time without losing track of its location. We believe this is overkill for many commercial applications. New and Exciting Applications for INS Lately, new and exciting applications have emerged. One example is to "fingerprint" or to track a particular motion. Actually, it is a multi-dimensional fingerprint in six variables and in all three room-coordinates. The simplest example is to mount our 2-INS to a car and then to maneuver the car through a well-defined motion on the road (a narrow turn perhaps). The INS has now sampled the complex fingerprint of this well-defined motion. Now, by changing something on the car, like the tires or the gearbox, and repeating the well-defined motion one immediately learns how the change affected the car, and a fingerprint of the new condition is available. The same advantage is achieved by changing the strings on a tennis racket or by tying the shoestrings harder on the running shoes. Furthermore, it is possible to fingerprint a specific driver or player as he passes through a particular curve or difficult passage on the road. By comparing this driver s INS fingerprint to other drivers, or even to himself at different times, the driver can learn how to improve. The signals of the INS can uniquely tie the action of a driver to performance on the track, or accurately describe a tennis serve. By mounting two independent 2-INS to the hull of a ship, it becomes possible to observe the relative motion of the different parts of the hull. Anomalous and unwanted motions can be monitored.

4 Page 3 (4) INS Limitations Finally, even such elusive qualities as driver s comfort can now be more objectively measured and described. All INS suffer from internal errors that limit their performance. Hence, it is not possible to measure the acceleration or position with arbitrary accuracy. There will always be a system-drift that degrades the performance over time. Sooner or later any INS will loose track of where it is. Large INS systems on submarines, where the sensors are big and heavy, can be very accurate and are able to track the position under water for days and weeks with no more than small errors. INS on commercial jets need only be accurate to within tens of kilometers at the end of a transatlantic flight. The long-term performance can be improved by combining the INS with other information and sensor signals. For example, encoders on wheels or position estimates from GPS units, can control the otherwise accumulating position error, while the INS maintains its tracking capability of small and delicate maneuvers. The present status of the Imego 2-INS The Imego 2-INS, Figure 1, is primarily designed to track extremely difficult motion in all dimensions. It permits tracking motions with accelerations as high as H50g, with mg resolution, in all three directions (x, y, z), and with rotational velocities of H3000º/s (~10 revolutions/s) around all three axes. It tracks very rapid changes of motion, as the system bandwidth is several hundred Hertz. This dynamic range is significantly larger than what can be expected in an automobile or even an airplane. Under these difficult conditions it can track position and orientation parameters with accuracy better than a centimeter and fractions of one degree, after about ten seconds. The performance, or the maximum length of tracking time, greatly increases if the motion is smoother, for example slower, less violent or somehow predictable. Another immensely simplifying fact, for a car, is that violent accelerations never occur in more than one direction at one time. Not even a racecar accelerates hard, beyond a few g s, in any given direction anyway. It is reasonable to believe that a tailored INS, for whatever application, will yield superior data to the current system that is geared toward one specific application. The Imego system is designed to compile information from an array of sensor sources, for example, rpm-meters, tachometers, ignition information, GPS units, speed radars, or external cameras. This additional information, again, dramatically improves the accuracy of the INS. Our top-notch INS sensors guarantee an accurate measurement of different types of complex low frequency vibrations, angular vibrations, and other anomalous movements.

5 Page 4 (5) 50 mm Figure 1. The side of this INS cube is about 50mm. Specifications The Imego 2-INS is custom built to be small and light, in addition to operating at absolute highest technical performance. The system is geared toward a very high range in motion (H50g and H3000º/s) combined with a generous frequency bandwidth (0-200 Hz). The sensor signals are further processed by dedicated INS software, where raw signals are transformed into unique information about a motion. The specifications for the current version are given in Table 1. Table 1. General specifications for a typical Imego 2-INS. Notice the very high range of motion and high dynamic resolution. Measured quantity magnitude unit weight 94 gram size 50x50x50 mm power consumption <1 W max acceleration in x, y, z H50 g max rot. velocity around x, y, z H3000 º/s system noise level (accelerometer) 10-4 g/ahz system noise level (gyroscope) 0.02 º/s/aHz bandwidth Hz sample speed >1000 Hz

6 Page 5 (6) The INS measures and/or computes eighteen variables that uniquely define a motion, see Table 2. All variables are resolved in time and recomputed into the only useful reference frame, a coordinate frame fixed with respect to an outside observer. Hence, all motion of a car, or a high-jumper, is measured in coordinates that do not move together with the object. Table 2. The eighteen variables of a 2 -INS that are resolved in time and space. The six independent inertial sensors measure the primary quantities: acceleration and rotational velocity. quantity directions unit acceleration measured x, y, z g, (m/s 2 ) velocity computed x, y, z m/s position computed x, y, z m angular acceleration computed x, y, z º/s 2 rotational velocity measured x, y, z º/s orientation computed x, y, z º

conditions (see Figure 2, stage 2). Hence, the 2-INS demonstrator that is photographed on the cover (stage 1 in the figure), and described in this brochure, is already technically surpassed.

7 Page 6 (7) Future 2-INS development at Imego The INS program at Imego is continuously improving and getting stronger. Presently, the driving force is a multi million-dollar commercial contract with a large US company, where Imego is contracted to develop a unique state-of-the-art 2-INS for extremely difficult conditions (see Figure 2, stage 2). Hence, the 2-INS demonstrator that is photographed on the cover (stage 1 in the figure), and described in this brochure, is already technically surpassed. Both systems are commercially constructed, employing all commercial sensors and production methods. 3 rd generation demonstrator 1 GENERAL - tracks, fingerprints and records objects in motion - provides unbiased record of position, orientation, velocity and acceleration - records all degrees of freedom at 1000 Hz 3 3 YEARS 1 cubic inch + CD-ROM 100 grams, 8 in 3 currently fully operational in native environment 2 Prototype operational Q grams, 3 in 3, 24-bit A/D, RAM buffer, wireless data transfer, flash card data storage Figure 2. Evolution of Imego s 2 -Inertial navigation System. The advanced future concept we strive toward is a super small and generally applicable system, such as in stage 3 in Figure 2. This system will be possible to mount almost anywhere, and it will transfer data by a wireless link to a nearby computer. All necessary software will fit on an accompanying CD-ROM.

Page 7 (8) The development aims toward custom design, real time data acquisition, and control. We utilize flex-rigid assembly technology to uniquely shape the hardware.

8 Page 7 (8) The development aims toward custom design, real time data acquisition, and control. We utilize flex-rigid assembly technology to uniquely shape the hardware. The real time sensor information permits direct control of maneuvers and processes. A special unit within Imego is dedicated to INS software, optimizing algorithms and customizing INS to fit specific applications. This unit also holds a broad INS patent, as well as various relevant sensor patents. Imego presently has a well-developed patent portfolio in this area, but even more importantly we have the technological advantage that most likely can be counted in years. Imego also has another huge advantage over US based companies, we are not bound by the stringent US export regulations. It is difficult for a US company to export any product, containing a gyroscope, which has not been previously federally approved. Furthermore, Imego is developing the next generation gyroscopes that will push the limits of MEMS gyros to a new level. This development is contracted by Saab Bofors Dynamics, and the application is for military avionics. Included in this effort is a dedicated application specific circuit (ASIC) that will substitute the discrete components, for the control of the gyro, into one chip. The first version of this ASIC will have tape-out in Q The last building block of the Imego INS program is a three-axis accelerometer (see Figure 3). It will be the first commercial accelerometer that measures all three directions on one chip. The production method solves many alignment problems and dramatically reduces the footprint. Several other advantages make this design valuable, for example low cross-axis sensitivity. The processing is simple and the design is suitable for force feedback implementation. Figure 3. The mass elements of Imego s patented three-axis accelerometer.

9 Page 8 (9) What can be done in six months? Imego is actively working on shaping our 2-INS to fit different types of objects or spaces. One example is our advanced concept of an 2-INS that fits inside a narrow cavity, less than 20mm wide. Our packaging group works with all commercially available technologies, carefully selecting the process or manufacturer that solves the problem along given specifications. The size and weight can be reduced to 1/2 of today s system. Several systems can be built and synchronized together. The INS can be fused with other sensor signals, to enable positioning for long periods of time while retaining the resolution of delicate maneuvers. What can be done in twelve months? Conclusions One year is enough time to decrease the volume to 1/5 and the weight of the complete system to 1/3. Further reduction necessitates developing an Application Specific Circuit (ASIC), which takes about 18 months. This super 2-INS would also contain a complete data acquisition system, removing the need for a wire and external data capture equipment. Several 2-INS can be made to communicate with each other, tracking complex systems with independent parts. Another development is to tailor the technical performance to a specific application. This may involve a different choice of sensors, change of electronic solutions, and most likely specifically developed software. This type of INS-development promises to dramatically improve the performance, including accuracy and duration of the tracking time. The Imego 2-INS program focuses on accurate tracking of any type of motion, using exceedingly smaller and lighter sensor systems. One of the most useful applications is to fingerprint a particular motion, or particular equipment. INS provides all the necessary variables to completely specify any motion. The current Imego 2-INS is developed for conditions much more severe than what is likely in for example automobiles, or in many sports applications. The accuracy and duration of tracking time can be expected to improve greatly when harnessed for customized applications. Within a few months, we can tailor the form factor of the unit and reduce its size and weight by half or we can conduct an in-depth feasibility study of the 2-INS for a customer specific environment. In one year it is possible to develop a custom 2-INS for a specific task, tracking position and angles with unmatched accuracy. This system would represent the state-of-the-art in 2-INS. Used as a testing and research tool the 2-INS promises to, without delay, bring results and savings to the customer.

Inertial Navigation Systems

Inertial Navigation Systems Kiril Alexiev University of Pavia March 2017 1 /89 Navigation Estimate the position and orientation. Inertial navigation one of possible instruments. Newton law is used: F =