Automatic cruising speed controller for an automotive vehicle

Abstract

An aromatic cruising speed controller for an automotive vehicle adjusts the throttle valve of the engine to perform the constant speed cruising control of the vehicle. A running resistance detector unit 18 calculates the running resistance R from the output torque T of the engine, the vehicle acceleration .alpha., and the engine set-up condition including the gear ratio G. During the transient period immediately after the cruising control is commenced or resumed, the torque T0 of the engine which is necessary for attaining the target vehicle speed V0 is determined from the running resistance R, the gear ratio G, and the target throttle position is determined on the basis of this torque T0. Under the steady state, on the other hand, the throttle position is controlled in accordance with the proportional plus integral control method, such that the deviation .DELTA.V of the vehicle speed V from the target vehicle speed V0 is reduced to zero. The drop or the overshoot of the vehicle speed during the transient period is thus suppressed. Alternatively, the proportional and the integral control gains of the throttle position are varied in accordance with the variation of the running resistance R. The response delay and the hunting of the vehicle speed under the uphill/downhill driving condition can thus be suppressed.