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    A temperature-compensation technique for improving resolver accuracy
    (2021-09-01)
    Petchmaneelumka, Wandee
    ;
    Riewruja, Vanchai
    ;
    Songsuwankit, Kanoknuch
    ;
    Rerkratn, Apinai
    Variation in the ambient temperature deteriorates the accuracy of a resolver. In this paper, a temperature-compensation technique is introduced to improve resolver accuracy. The ambient temperature causes deviations in the resolver signal; therefore, the disturbed signal is investigated through the change in current in the primary winding of the resolver. For the proposed technique, the primary winding of the resolver is driven by a class-AB output stage of an operational amplifier (opamp), where the primary winding current forms part of the supply current of the opamp. The opamp supply-current sensing technique is used to extract the primary winding current. The error of the resolver signal due to temperature variations is directly evaluated from the supply current of the opamp. Therefore, the proposed technique does not require a temperature-sensitive device. Using the proposed technique, the error of the resolver signal when the ambient temperature increases to 70 °C can be minimized from 1.463% without temperature compensation to 0.017% with temperature compensation. The performance of the proposed technique is discussed in detail and is confirmed by experimental implementation using commercial devices. The results show that the proposed circuit can compensate for wide variations in ambient temperature.
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    Temperature Compensation for Transformer-type Transducer
    (2021-01-01)
    Songsuwankit, Kanoknuch
    ;
    Riewruja, Vanchai
    ;
    Watanachaturaporn, Pakorn
    ;
    Rerkratn, Apinai
    ;
    Petchmaneelumka, Wandee
    A novel technique to compensate the temperature effect of a transformer-type transducer is proposed in this paper. The effect of the ambient temperature on the transformer-type transducer is investigated from a primary-winding current. The advantage of the proposed technique is that the temperature effect is compensated without requiring a temperature sensor, making it suitable for applications in robotic and automation systems operated in harsh environments. The primary-winding current of the transducer is generated using a second-generation current conveyor (CCII). The excitation signal of the transformer-type transducer is driven by the CCII and the current flowing through the primary winding is transferred to an output signal of the CCII. The deviation of the primary-winding current due to the temperature effect is evaluated from the output signal of the CCII. The temperature effect on the transducer is manipulated by a closed-loop principle using a subtract-and-sum action instead of a traditional proportional-plusintegral action to eliminate the deviation of the primary-winding current. Therefore, the temperature effect on the transducer is compensated. A linear variable differential transformer (LVDT) is used to demonstrate the proposed technique, whose performance is discussed in detail and confirmed experimentally. All devices used in this experiment are commercially available. Experimental results show that the measured error of the output signal from the LVDT at 70 C can be reduced from 6.2% without temperature compensation to 0.06% by using the proposed technique, which has the advantages of a low cost, simple configuration, and high performance.
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    Temperature Compensation For V/F Converter
    (2012-03-01)
    Riewruja, Vanchai
    ;
    Petchmaneelumka, Wandee
    ;
    Rerkratn, Apinai
    ;
    Songsuwankit, Kanoknuch
    In this article, a method to compensate the temperature effect of voltage to frequency converter (V/F) is presented. Realization technique is based on the use of fre-quency to voltage converter (F/V), which provides the inverse transfer characteristic of V/F converter, in feedback path. The conversion gain of the proposed scheme is identical as a simple V/F converter without effect from feedback con_guration. The frequency derivation due to the change of temperature from 25°C to 60°C can be improved more than 86.4%. Experimental results demonstrated the proposed principle using commercial devices is also included. © 2012 ICIC International.
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    Analog multiplier using operational amplifiers
    (2010-01-01)
    Riewruja, Vanchai
    ;
    Rerkratn, Apinai
    Simple circuit technique for implementing four-quadrant analog multiplier has been presented. The proposed circuit requires only operational amplifier (opamp) as the active element. The realization method is based on the quarter-square technique where a square is provided from the inherent quadratic behaviour of class-AB output stage of opamp. Experimental results showing the circuit performance are described. The wore-case linearity error and total harmonic distortion for maximum operating range are about 0.23 and 1.02%, respectively.