Speed up servo system

Issue & Solution

Issue ...

Accuracy of the servo system is necessary, even at higher speeds.

As robots become more secure and fault-predictive, developers will want to build even faster servo systems without compromising performance.

Reviewing the current detection system configuration is necessary in response to a robot's evolution.

Many of AKM's robot and motor manufacturers have problems developing new models. Response speeds of conventionally used ΔΣ A/D converters, (ADCs), are becoming insufficient as the current control loop needs to be faster relative to the the system speed increase. Of course, the response speed issue can be resolved by using a fast successive approximation ADC. However, in this case, an averaging process is necessary for the system since switching noise cannot be averaged like a ΔΣ type.

Then what is our solution…

Real-time response + Noise suppression A/D converter

Speed up servo system

Maintaining high S/N of the inverter phase current, achieving high precision servo

Benefits for both customers using ΔΣ ADCs and using successive approximation ADCs

AKM's new ADCs maintain the high accuracy of phase current S/N performance even with a high speed servo system since the switching noise is suppressed by the averaging process in the LSI similar to a ΔΣ ADC.

For customers currently using successive approximation ADCs, this noise suppression function can improve the accuracy of the servo system while maintaining responsiveness. In addition, our compatible lineup enables quick replacement of existing ADCs.

This series is a 16-bit/14-bit 2ch ADC, with oversampling A/D conversion, outputting a signal from 0.5 to 1.1 MSPS. The noise suppression function minimizes high frequency noise included in the analog input signal. The noise suppression amount can be changed. Different output interface options are also available.

The AK925X series is a 2ch A/D converter housed in an ultra-small 3mm x 3mm QFN package.

High Speed Performance and Noise Suppression Function

The AK925X series suppresses high frequency noise included in analog input signals with oversampling A/D conversion which is the same as a ΔΣ ADC with real time response. (An SAR ADC accomplishes real time response but is not able to suppress noise. In the opposite way, a ΔΣ ADC can suppress noise, but has a response delay.)

The noise suppression amount of the AK925X series can be selected at four levels.

Pin Compatible to Existing ADCs

The AK925X series are pin compatible with existing 14bit/16bit SAR ADCs from other companies.

Lineup

A/D Converter with 1Msps Conversion Rate

Small + High Accurate New Industrial ADC

ZDS A/D Converter

Normally, SAR A/D converters are used in a system that needs real time response for motor control encoders. However, it is not easy to construct a system or improve characteristics with an SAR A/D converter since its acquisition time becomes shorter and the input capacitance becomes larger when seeking high speed and high accuracy performance. 

Zero Latency Delta Sigma, (ZDS), ADCs: AK9232/AK9233/AK9234 are new concept A/D converters that have both SAR's high accuracy and Delta Sigma's high linearity. 

An 18-bit, 1.1MHz 2ch ADC: the AK9232, realizes low input capacity and long acquisition time while maintaining high speed and high accuracy. It is housed in a 4mm x 4mm package, the smallest class in the world, shrinking system construction and improving characteristics. 

16-bit and 14-bit versions of the AK9232, the AK9233 and the AK9234, are also line upped.

Contribute to Improving Accuracy and Speed of Your System

Designing Low Input Capacitance with Long Acquisition Time

Longer acquisition time and lower input capacitance are accomplished with the ZDS architecture that is developed from many years' experience from AKM in Mixed-signal LSI technologies, comparing to a general SAR ADC. The ZDS architecture reduces ADC amplifier load. The AK9232/3/4 contributes to improving accuracy and speed of your system.

Realizing Low Input Capacitance and Long Acquisition Time

Offset/Gain/Phase Adjustment Function

Offset/Gain/Phase adjustments for converted signal are available on each channel independently.

Polar Coordinate Output Function

The AK9232/3/4 is capable to output the polar coordinate, (angle, "θ", moving radius,"r"), when the cosine wave and sine wave are input to the CH0 and the CH1, respectively, from the result of simultaneous conversion of the input signal of the CH0 and the CH1.

A digital output reference module of current sensor, that is suitable for AC Servos, Robots and General Inverters, is available.