A piezoelectric dynamometer can produce thermal forces because of temperature fluctuations, thus affecting measurement precision. To investigate the influence of the thermal force on the dynamometer, this article proposes a hypothesis of decreasing the conduction power and establishes the function of a thermal force over time in an ordinary dynamometer based on the heat conduction differential equation. A novel double-sensor thermal compensation dynamometer is designed, with static calibration in constant temperature and force/heat coupling experiments, to solve the problem of the thermal force. The experimental results indicate that the nonlinearity and repeatability of the double-sensor thermal compensation dynamometer are less than 1% full scale (FS) of the static calibration at a constant temperature; in the force/heat coupling experiments, at a heating rate of 0.4 ℃/s to 110 ℃ with a loading force of 500 N, the maximal output deviation is less than 1.06% (FS), realizing the unidirectional thermal force compensation of the structure. The double-sensor thermal compensation dynamometer can be utilized in sharp temperature fluctuations environment, like rocket engine forces measurement.
Investigation of the thermal compensation behaviour of zero-point clamping systems
