PURPOSE: To save energy by selecting the output of a speed limiter when the absolute value of a difference between a steering angle commanding rate and a feedback gain based upon an actual pump swash plate angle rate is above a predetermined value and the output of a speed limiter bypass circuit when the absolute value is below the predetermined value.
CONSTITUTION: A steering angle commanding rate θ0 and a gain K of a swash plate angle feedback gain adjuster 3 are transmitted to a relay switching arithmetic unit 7, which selects, as a pump swash plate angle command, the output 0' of a speed limiter 1 by a switch 8 when an absolute value of the pump swash plate angle commanding rate is above a predetermined value, and selects the output 0 sent through a speed limiter bypass circuit 9 when the pump swash plate angle commanding rate is below the predetermined value. In this way, rapid control of the pump swash plate angle is performed by the speed limiter 1 and minute steering angle control is performed by sending 0 directly bypassing the speed limiter, thereby to obtain close steering for minimized operating path and saved fuel costs.
NONAKA MITSUYUKI
ABE TSUGUYA
MISHINA HARUHIKO
