Sensors convert nonelectrical physical or chemical quantities into electrical signals. The behavior of semiconductor sensor devices is modeled, under a series of assumptions, by a system of nonlinear partial differential equations and associated boundary and input value conditions. For such sensors, it is essential to solve numerically at least some of the equations in order to obtain a meaningful result describing environmental conditions encountered by the sensor. Mechanical sensors also suffer from some of the same issues relating to nonlinearity and associated boundary and initial value considerations.
When the desired result is determined by the integration of sensor output over time, errors of bias scale, and nonlinearity occur. Mathematical algorithms are used to improve the accuracy of the result by correcting for such errors of bias, scale and nonlinearity.
The present invention relates to methods and devices of determination of an input signal which changes in time as well as of its integral value.
Methods are known of the above mentioned general type and disclosed for example in Inventor's Certificates of the USSR 1,453,418 and 1,541,635. In accordance with the method and device disclosed in these references, integration is performed to a given value of the integration result. This objective is presented for example in inertia systems of targeting, for turning off an engine when a rocket reaches a desired speed V.sub.r. The input signal in this case is an acceleration which is measured by accelerometer, and its inaccuracies are a main source of error of the system as a whole. The device includes a convertor 1 for a frequency of pulse sequence, a frequency multiplier 2, an integrator or pulse counter 3, a source of reference signals 4, keys 5 and a control device 7. A code corresponding to a desired value of speed is introduced into the pulse counter by integration of reference signals (accelerations) during a time corresponding time interval. The values of the reference signals can be obtained by turning a sensitivity axis of the accelerometer relative to a local vertical. Then, during measurements of the input signal which is the acceleration during a flight, an inverse integration is performed. In other words, the pulses from the convertor, multiplied many times by the frequency multiplier are deducted in the counter from the code obtained during the time of direct integration when the counter was operating for addition of the reference signals. A system of equations was used to determine the reference signals and time intervals. The nature of change of the input signal was approximately known beforehand, and therefore an initial moment of the input signal was calculated. Zeroing of the pulse counter is a signal that the speed reached the desired value. The above described method has a high accuracy. However, it has some disadvantages, namely the fact that the high accuracy is guaranteed in only one point and not along the whole scale of speed changes. This values must be known in order to determine of the location of a rocket. The known method and device are not always technically implementable since it is necessary that one reference signal is greater and the other is smaller than an average value of the input signal. However, the acceleration can reach a few g while on the ground during giving of the reference signals not always there is a standard of acceleration more than 1 g.