TI's Advanced Microprocessor Steers Automotive Designers to Eliminate Hydraulics

Automotive hydraulic subsystems, some of the most maintenance intensive parts of any car, could soon be eliminated, thanks to a powerful new microprocessor from Texas Instruments (TI). The new electronic microprocessor combines an extensive set of motor control features with enough processing power to execute complex control equations needed for direct drive electric motor control of steering, braking, and other automotive subsystems. Because these computer chips reduce the need for automotive designers to use hydraulic subsystems, they can make cars cheaper and more energy efficient.

Known as a digital signal processor, or DSP, this advanced computer chip adds and multiplies tens of millions of complex formulas every second. A DSP chip is 10 to 50 times more powerful than other computer chips in handling math intensive tasks, and it enables numbers to be processed in "real time." TI is the world's leading provider of DSP solutions, having patented its first DSPs in 1982.

A Revolution in Automotive Control

The rapid growth of DSPs, a market expected to reach $9 billion by the year 2000, is enabling the creation of new and improved products in industries such as automotive. Because TI's TMS320C240 DSP allows variable speed control, inexpensive brushless motors can be connected directly to actuators that are today controlled via variable pressure hydraulic fluid. Hydraulic subsystems have long been mainstays of automotive control systems, but their numerous disadvantages make their elimination from the automotive environment desirable. Control systems that use the 'C240 in direct-drive electronics can be more reliable and cleaner, requiring no highly pressurized hydraulic fluid and doing away with the engine load incurred when pressure must be delivered to hydraulic systems. DSP-enabled electronic controls may also weigh far less than their hydraulic predecessors, can be easier to install and maintain, and can occupy less physical space, placing fewer design constraints on automotive engineers.

Because the 'C240 DSP is an "intelligent" control processor, all electronic control systems enabled by the chip can be programmed to behave far more flexibly than a traditional hydraulic system. For example, a 'C240-based electronic power steering subsystem can be programmed to exhibit a variable steering profile, with relatively slack steering response at very low speeds, and tight, sports car-like response at highway speeds. Electronic brake controllers use the 'C240 to directly drive high-torque switched reluctance motors, allowing a localized, intelligent control loop for advanced anti-lock brake systems. Other areas where the intelligence of the 'C240 can be applied include active suspension control, and window motors programmed to detect current overload, stopping the closure of a window whose travel might otherwise inadvertently injure a passenger.

The Power of a DSP

TI's breakthrough 'C240 DSP controller is a DSP solution that includes a 20 MIPS processor CPU that runs sophisticated motor control formulas, a specialized motor control circuit called an "event manager," plus a comprehensive group of motor control peripherals, all on a single microprocessor.

In addition to the DSP core, the 'C240's unique motor control event manager directly supports generation of pulse width modulated (PWM) outputs to drive the motor power amplifier, and integrates motor control features that include timers, comparators, dead-band generation logic, a state space vector generator, and direct inputs for optical encoders. Additional peripherals include serial interfaces, analog-to-digital converters, digital input and output lines, a low-voltage detector, and on-chip memory.

The processing power of the 'C240 DSP allows math intensive motor control algorithms, which enable sensorless and adaptive controller designs to be used in mainstream product designs for the first time. System cost can be lowered by reducing part count and through the use of inexpensive motors such as DC brushless, switched reluctance, and AC induction. A 'C240-based system can also provide improved energy efficiency and reliability along with reduced vibration and noise.

DSP Enables Use of Low-Cost Brushless Motors

Brushless motors offer many advantages over traditional brush-type motors including lower cost, lighter weight, and reduced maintenance, but they require real-time execution of mathematically intensive control algorithms for robust control. The 'C240 supports this need by enabling the use of complex DSP-based formulas which allow precise, adaptive control of brushless motors with the ability to reduce the number of expensive sensors for position and loading feedback.

'C240-based motor controllers can provide precise torque control and speed regulation of brushless motors, and superb response to rapid speed or load changes, but without the weight, high maintenance costs, and energy consumption of a more expensive DC brush motor or hydraulic system. These 'C240 controllers for brushless motors can deliver full torque, even at standstill, and because they are brushless, are well suited to the harsh automotive environment.

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