New magnetic position sensors from ams feature technology capable of producing extremely accurate angle measurements of rotors spinning at high speed. The new ‘47 series’ includes the AS5047D, AS5147 and AS5247 with DAEC (Dynamic Angle Error Compensation), a patent-pending technology developed by ams that eliminates the measurement error attributable to propagation delay.
The AS5047D is ideally suited for industrial applications like robots and encoder modules; the AS5147 is an AEC-Q100 qualified part for automotive applications such as electronic power steering and pumps; and the dual-die AS5247 (also AEC-Q100 qualified) is well suited for automotive applications requiring the highest level of functional safety compliance. All three parts are specified with a maximum ±0,17&de; angle error (excluding integral non-linearity).
This precision measurement results from the DAEC algorithm, which performs error compensation internally and responds automatically to changes in the speed of rotation.
Traditional magnetic rotary position sensor ICs suffer from a propagation delay (typically 100 – 200 μs) as they convert raw measurements of magnetic field strength at their embedded magnetic elements into digital angle measurements. During this delay, a spinning rotor’s angular displacement changes, so that its actual position when the digital output leaves the sensor differs from its measured position. The resulting error increases in a linear fashion with increases in the speed of rotation: for a propagation delay of 100 μs, at 1000 rpm the dynamic angle error is 1,2° and at 10 000 rpm it is 12°.
DAEC almost completely eliminates this source of error, dynamically compensating every measurement sample for the speed of rotation at the time the sample is captured. The 47 series sensors provide angle measurements accurate to ±0,08° at 7000 rpm, to ±0,14° at 12 000 rpm and to ±0,17° at 14 500 rpm.
With their high accuracy, the ICs are ideally suited to all motor control and angle measurement applications. In high-speed brushless DC (BLDC) motors and permanent magnet synchronous motors (PMSM), they enable better execution of the commutation scheme, resulting in higher torque and efficiency, lower torque ripple and smoother operation.
All three devices provide absolute position measurements as a digital PWM output, and UVW outputs for use in field-oriented commutation schemes. They also provide an incremental ABI output equivalent to the output of an optical encoder. This means an AS5047D can replace an optical encoder without requiring the user to change the software interface in the host system’s microcontroller or DSP.
The 47 series offers 14-bit resolution (to 0,022°) via the digital SPI output, and maximum resolution of 2000 steps per revolution in decimal mode and 2048 steps per revolution in binary ABI mode. Its differential sensing circuitry offers immunity to stray magnetic fields and enables the devices to be used in electrically noisy environments without any requirement for shielding.
For more information contact NuVision Electronics, +27 (0)11 608 0144, [email protected], www.nuvisionelec.co.za
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