Speed stage shifting of automatic transmission by composite control phases employing common target parameter

A method of controlling an automatic transmission of a vehicle for shifting from a first speed stage of a first reduction gear ratio to a second speed stage of a second gear ratio, said transmission comprising a speed change gear mechanism including gears and gear carriers as rotary members and hydraulically operated friction engaging means and adapted to provide various speed stages including said first and second speed stages according to selective engagement and disengagement of said friction engaging means, said friction engaging means including first and second friction engaging means, and said rotary members including a first rotary member whose rotation speed reflects an engaging condition of said first friction engaging means and a second rotary member whose rotation speed reflects an engaging condition of said second friction engaging means, comprising the steps of:

• detecting rotation speed of said first and second rotary members during the shifting between the speed stages;
• changing hydraulic pressure of said first friction engaging means during a first phase of said speed stage shifting so as to shift a first part of said speed change gear mechanism for contribution to shifting the reduction gear ratio from said first reduction gear ratio to said second reduction gear ratio with the rotation speed of said first rotary member following a first change performance curve calculated according to a first feedback control program, while changing hydraulic pressure of said second friction engaging means so as to shift a second part of said speed change gear mechanism for partly cancelling said contribution of said first part of said speed change gear mechanism to the shifting of the reduction gear ratio from said first reduction gear ratio to said second reduction gear ratio;
• and
• changing the hydraulic pressure of said first friction engaging means during a second phase of said speed stage shifting so as to make the rotation speed of said first rotary member follow a second change performance curve calculated according to a second feedback control program in continuity to said first change performance curve, wherein switching over from said first phase to said second phase is triggered according to a detection that rotation speed of said second rotary member traversed a threshold value which reflects an engaging condition of said second friction engaging means to effect a predetermined progress of said shifting of said second part of said speed change gear mechanism.