Automotive applications are known to impose quite harsh environmental conditions such as vibration, shock, temperature, and thermal cycling on inertial sensors. Micromachined gyroscopes are known to be especially challenging to develop and commercialize due to high sensitivity of their dynamic response to fabrication and environmental variations. Meeting performance specifications in the demanding automotive environment with low-cost and high-yield devices requires a very robust microelectromechanical systems (MEMS) sensing element. This paper reviews the design trend in structural implementations that provides inherent robustness against structural and environmental parameter variations at the sensing element level. The fundamental approach is based on obtaining a gain and phase stable region in the frequency response of the sense-mode dynamical system in order to achieve overall system robustness. Operating in the stable sense frequency region provides improved bias stability, temperature stability, and immunity to environmental and fabrication variations.

This paper describes a low-cost silicon vibratory gyroscope that tolerates a relatively large mismatch between the driving-mode and sensing-mode frequencies. The gyroscope is based on beam-mass structure and realized by one silicon proof mass and two beams for the driving and sensing mode. Piezoelectric actuation is used to produce a large driving mode vibration displacement (about 100 μm) with about 32 V peak-to-peak . Two tiny sensing beams are separated from the vertical silicon beam to increase the sensitivity while keeping the sensing-mode resonant frequency high. Piezoresistive and piezoelectrical sensing mechanisms are applied to two different gyroscopes. The gyroscope operating at 1-4 kHz is capable of sub-degree-per-second angular rate sensitivity without any vacuum package.

Commercialization of reliable vibratory micromachined gyroscopes for high-volume applications have proven to be extremely challenging, primarily due to the high sensitivity of the dynamical system response to fabrication and environmental variations. This paper reports a novel micromachined gyroscope with 2 degrees-of-freedom (DOF) sense-mode oscillator, that provides inherent robustness against structural parameter variations. The 2-DOF sense-mode oscillator provides a sense-mode frequency response with two resonant peaks and a flat region between the peaks, where the amplitude and phase of the response are insensitive to parameter fluctuations. Furthermore, the sensitivity is improved by utilizing dynamical amplification of oscillations in the 2-DOF sense-mode oscillator. Prototype gyroscopes were fabricated using a bulk-micromachining process, and the performance and robustness of the devices have been experimentally evaluated. With a 5.8mum drive-mode amplitude, the tested unit exhibited a measured noise-floor of 0.64deg/s/radic(Hz) at 50Hz bandwidth in atmospheric pressure. The sense-mode response in the flat operating region was also experimentally demonstrated to be inherently insensitive to pressure, temperature and DC bias variations

As BEI Technologies, Inc. transitioned from a low-volume, high-cost aerospace and defense supplier to a high-volume, low-cost automotive supplier for the Systron Donner quartz rate sensor gyroscope (GyroChip reg ) after the mid-1990s, a need to effectively manage mass customization without replicating the production line became an economic imperative. This paper describes the tools and techniques utilized to not only solve the problem economically, but provide several significant side-benefits as well. Starting from zero high-volume mass customization experience in 1996, Systron Donner can today accommodate dozens of configurations on the same high volume production line. In addition, the line can accommodate multiple small runs (dozens to hundreds of units per day) on the line concurrent with the normal production (several thousand units per day). These benefits are supplemented by additional capabilities to achieve traceability down to the component level, screen units with a performance grading technique, permanently store all manufacturing and test data, provide integrated statistical process control information, ensure proper process step sequencing and ensure correct labeling and shipment.

In the early 1990s, Systron Donner Inertial Division (SDID), a subsidiary of BEI Technologies, Inc., possessed a new solid-state rate gyroscope technology that had not yet matured or captured a significant market share. Even though some success had been achieved in defense missile applications, a strategy was clearly needed to further develop the technology and lay the foundation for future growth. The strategy search led to discovery of a leading edge automotive brake system application, which, in turn, led to a radical change in SDID design and manufacturing approaches as well as a dramatic increase in revenues. The resultant radical cost-reduction of Quartz Rate Sensor (QRS) components has benefit for both the automotive and the Aerospace and Defense (A&D) markets. Commonality of design and design techniques is leveraging high-volume, low-cost automotive components into low-volume A&D products.

After a severe downturn in its traditional aerospace and defense (A&D) markets in the early 1990s, Systron Donner Inertial Division (SDID), a subsidiary of BEI Technologies, Inc., decided to enter commercial markets with ground breaking new technology for a solid-state rate gyroscope, the Quartz Rate Sensor (QRS). The quartz Coriolis force technology was appropriate for a new automotive brake system application, but the company required radical changes in its operations to achieve successful penetration of the automotive market. After four decades exclusively in the A&D business, this decision had massive implications for the company's marketing and contracting approach, business system infrastructure, manufacturing operations, facility layout, quality system, supply-chain management, and engineering product development. Indeed, entry into the automotive market required changes that posed management challenges similar to a start-up company.

In 1835, the French engineer-mathematician Gustave- Gaspard de Coriolis (1792-1843) first described the inertial force now called the Coriolis effect. The effect is an apparent deflection of an object that moves within a rotating coordinate system. The object does not actually deviate from its path, but appears to do so because of the coordinate system motion. The effect is inherent in vibrating tuning fork structures, and is useful in detecting rotation rate. In the 1940s, the Sperry Gyroscope Company developed a tuning fork rate sensor called the Gyrotron, which demonstrated technical feasibility, but was not economically manufacturable. Cost-effective rate gyro production awaited availability of materials and processing technologies compatible with mass-production. Piezoelectric quartz and its high volume use in the crystal oscillator industry provided the right material for the tuning fork. Micromachining techniques, developed in the semiconductor industry since the 1950s, provided a bulk processing technique for a low cost Microelectromechanical System (MEMS) based tuning fork. In addition, mixed signal Application Specific Integrated Circuit (ASIC) technology provided the needed bulk processing and high-density packaging for the signal processing electronics [1]. In the early 1980s, General Precision Industries (GPI), a small R&D organization formed by crystal oscillator industry veterans, demonstrated a piezoelectric quartz tuning fork rate sensor. In 1986, the Systron Donner Corporation of Thorn EMI (now the Systron Donner Inertial Division of BEI Technologies, Inc.), acquired the rights to the promising technology with an exclusive worldwide license. These early beginnings have spawned a mass production of solid state rate gyro product family that has produced in excess of 4,000,000 sensors with an ever-improving price/performance ratio.