Abstract: A throttle valve controller achieves high output response to the smaller deviation of the actual opening from the demand opening of the throttle valve and achieves high control stability against the larger deviation. It has a preset data table containing proportional gain values and integral gain values of PID control in correspondence to deviation values in inversely proportional arrangement. During the transitional state of control system, a pair of provisional gain values are read out of the table in response to the deviation value: (step S3), these gain values are compared with those of the previous operation cycle and the smaller gain value pair are selected: (steps S4-S7), and the valve drive signal is calculated from the selected gain values:(steps S8, S11). Consequently, the controller achieves high output response to the smaller deviation due to the larger gain value and high control stability without the overshooting of valve movement against the larger deviation due to the smaller gain value.

Abstract: A step motor controller including a sampling program for sampling, at predetermined intervals, input target values that represent a position of the step motor. The difference between the sampled target value and a rotational position of the step motor is obtained. A step motor accelerating and decelerating program accelerates the step motor upon finding the difference between the sampled target value and the current position of the step motor is greater than a set value. When the difference is less than the set value the step motor is decelerated. The predetermined sampling time does not correspond to the natural frequency of the step motor system or to a period corresponding to a fractional multiple of the natural frequency.

Abstract: A controller for a step motor which permits the actual step number of the step motor to properly follow up the target step number may be varied with time. The controller temporarily determines a duration shorter than an actually derived duration, and checks the target step number again when the temporarily determined duration has elapsed. If the target step number has not changed, the actually derived duration is considered as a finally determined duration, while, if the target step number has changed, the duration of energization is re-derived from the changed target step number.