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Compensation Method for Thermal Drift of Voice Coil Motor Torque

IP.com Disclosure Number: IPCOM000035266D
Original Publication Date: 1989-Jun-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 47K

IBM

Related People

Miwa, Y: AUTHOR [+2]

Abstract

Disclosed is a compensation method to cancel thermal drift of a VCM (voice coil motor) torque by using the resistor which has a specific TCR (thermal coefficient of resistance).

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Compensation Method for Thermal Drift of Voice Coil Motor Torque

Disclosed is a compensation method to cancel thermal drift of a VCM (voice coil motor) torque by using the resistor which has a specific TCR (thermal coefficient of resistance).

The VCM is used as an actuator drive element which translates coil current into force or torque an shown in Equation 1 below. F = k * I (1) where F = torque, k = torque coefficient and I = coil current.

The torque coefficient 'k' depends on temperature. Let 'k(T)' be the function of temperature (T). F = k(T) * I (2)

The 'k(T)' has negative correlation to temperature and it can be assumed as a linear function of temperature on all ranges of the operating temperature (see Fig. 1).

(Image Omitted)

As seen from Equation 2, the effect of temperature can be canceled with coil current 'I(T)' which is the function of temperature (T) and is in inverse proportion to 'k(T)'.

Specifically, the thermal drift of VCM torque is cancelled by using a VCM drive circuit shown in Fig. 2. In Fig. 2, R1 has no TCR, and R2 has a specific TCR whose value is negative to the thermal coefficient of VCM torque. However, the temperature around R2 is near that around VCM.

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