Embedded Systems October 2000 Vol13_11

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American RAISONANCE response of the motor starts out slowly due to the time constant, but once that is out of the way the motor posi- tion ramps at a constant velocity. Precision actuator Introducing American Raisonance. Your new supplier of development tools for the Philips XA, 8051 , and ST6 microcontroller fami lies. Packages available with assembler, compiler, simulator and utilities for the Philips XA. Web distributed for immediate installation. One year technical support included in purchase. " Available individually or combined with XA tools. Source Code compatible with Keil 8051 tools for easy migration to XA. FIGURE 3 Motor and gear position vs. time Free assembler and simulator. Optimizing compiler including RIDE and utilities for program development. It is sometimes necessar'y to control the position of something very pre- cisely. A precise positioning system can be built using a freely movi ng mechan- ical stage, a speaker coil (a coil and magnet arrangement) , and a non-con- tact position transducer. You might expect to see this sort of mechanism stabi lizing an element of an optical system, or locating some othe r piece of equipment or sensor. Figure 4 shows such a system. Software commands the current in the coil. This current sets up a magnetic fi eld that exerts a force on the magne t. The magnet is attached to the stage, which moves with an acceleration propor- tional to the coil current. Finally, the stage position is monitored by a non- contact position transducer. With this an-angement, the force on the magnet is independent of th e stage motion. Fortunately this isolates the stage from ex te rnal effects. FIGURE 2 'A voltage driven motor and gear train +----,r Ar Motor + 0.8 1: 'iii 0 For CAN development, American Raisonance also distributes IXXAT CAN products and libraries for CAN-Open and DeviceNet. Call today for introductory 877-315-0792 a.. c: 0.6 1, . ~ , I ! 0.4 1' 0.2 ° -- o ." .. ., " ' : " ' 0.2 0.4 Time 0,6 , ,~ : , , .. .. .. , , .. " ., , ' : , , , , , , .. ~ " , , , , , .' , , , I - Input - - • Motor Position ' 0,8

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