the present invention relates to electric vehicles and , more particularly , hybrid electric vehicles ( hevs ). fig1 demonstrates just one possible configuration , specifically a parallel / series hybrid electric vehicle in a “ split ” configuration . in a basic hev , a planetary gear set 20 mechanically couples a carrier gear 22 to an engine 24 via a one - way clutch 26 . the planetary gear set 20 also mechanically couples a sun gear 28 to a generator motor 30 and a ring ( output ) gear 32 . the generator motor 30 can act to start the engine 24 , acting as a combined starter / alternator . the generator motor 30 also mechanically links to a generator brake 34 and is electrically linked to a battery 36 . a traction motor 38 is mechanically coupled to the ring gear 32 of the planetary gear set 20 via a second gear set 40 and is electrically linked to the battery 36 . the ring gear 32 of the planetary gear set 20 and the traction motor 38 are mechanically coupled to drive wheels 42 via an output shaft 44 . the second gear set 40 can include a transmission 60 . the transmission 60 can have a plurality of gear ratios that are selectively controlled by a transmission control unit ( tcu ) 62 . a gear ratio shift in an automatic transmission generally has two phases , a torque transfer phase and a speed ratio phase . during the torque transfer phase , the engine 24 torque is matched to transmission 60 torque at the new gear ratio . following the torque transfer phase , the engine 24 speed is allowed to adjust to match the transmission 60 speed . this speed matching is the speed ratio phase . the planetary gear set 20 , splits the engine 24 output energy into a series path from the engine 24 to the generator motor 30 and a parallel path from the engine 24 to the drive wheels 42 . engine 24 speed can be controlled by varying the split to the series path while maintaining the mechanical connection through the parallel path . the traction motor 38 augments the engine 24 power to the drive wheels 42 on the parallel path through the second gear set 40 . the traction motor 38 also provides the opportunity to use energy directly from the series path , essentially running off power created by the generator motor 30 . this reduces losses associated with converting energy into and out of chemical energy in the battery 36 and allows all engine 24 energy , minus conversion losses , to reach the drive wheels 42 . a vehicle system controller ( vsc ) 46 controls many components in this hev configuration by connecting to each component &# 39 ; s controller . an engine control unit ( ecu ) 48 connects to the engine 24 via a hardwire interface . all vehicle controllers can be physically combined in any combination or can stand as separate units . they are described as separate units here because they each have distinct functionality . the vsc 46 communicates with the ecu 48 , tcu 62 , as well as a battery control unit ( bcu ) 50 and a transaxle management unit ( tmu ) 52 through a communication network , such as a controller area network ( can ) 54 . the bcu 50 connects to the battery 36 via a hardwire interface . the tmu 52 controls the generator motor 30 and traction motor 38 via a hardwire interface . the control units 46 , 48 , 50 , 52 and 62 , and controller area network 54 can include one or more microprocessors , computers , or central processing units ; one or more computer readable storage devices ; one or more memory management units ; and one or more input / output devices for communicating with various sensors , actuators and control circuits . the strategies of the present invention can be embodied in a computer readable format programmed in one or more of the computing devices described above . fig2 illustrates a strategy for using a generator during throttle back - out transmission up - shifts to reduce torque reversals for an hev . the strategy starts at step 100 and proceeds to step 101 , where the strategy monitors vehicle system inputs . vehicle system inputs can include throttle position , vehicle speed , transmission 60 gear ratio , engine 24 rotational velocity and generator motor 30 rotational velocity . following step 101 , the strategy proceeds to step 102 , where the strategy determines whether a throttle back - out condition exists . this determination can be based on the rate of change of the throttle position . if no , the strategy returns to step 100 . if yes , the strategy proceeds to step 104 , where the tcu 62 indicates that an up - shift is required . following , step 104 , the strategy proceeds to step 106 . at step 106 , a rotational velocity of the engine 24 is detected . following step 106 , the strategy proceeds to step 108 . at step 108 , the generator motor 30 acts to maintain engine 24 rotational velocity at a preselected threshold above the detected engine 24 rotational velocity during the transmission 60 up - shift . the preselected threshold can be selected based on the rotational - velocity of the engine 24 and the gear ratio of the transmission 60 . the generator motor 30 receives a generator motor 30 speed control command to maintain engine 24 rotational velocity at the preselected threshold during the torque phase of the transmission 60 up - shift . the generator motor 30 can be operated in either a closed - loop control mode or an open - loop control mode . in open - loop control , a sequence of commands is carried out irrespective of the consequences . the magnitude of the control , i . e ., the amount of adjustment applied to the system , can be based on a set of operating conditions . in contrast , closed - loop control involves the use of feedback to help insure a desired set of conditions is met . the magnitude of the control can be based on the difference between the feedback signal and the desired condition . for the present invention , closed - loop control allows sensing of when to terminate the generator motor 30 speed control command . closed - loop control can generate a speed error signal that is used to adjust the generator motor 30 torque . the speed error signal will be zero or negative when the transmission 60 up - shift reaches the end of the torque transfer phase . the closed - loop control can also be configured to only output positive or zero values . when so configured , the closed - loop control effectively clips outputs that would result in negative generator motor 30 torque to zero . thus , the generator motor 30 can only increase the engine 24 rotational velocity . this type of control is referred to as uni - direction speed control . uni - directional speed control is not available in other types of control systems , namely , dashpot controls , known in the art . other forms of closed - loop control are also known in the art . the strategy can also operate in open - loop control . look up tables can be used to generate the generator motor 30 speed control command . another form of open - loop control can include generating the generator motor 30 speed control command from a transmission 60 rotational velocity signal . other forms of open - loop control are also known in the art . fig3 illustrates in graphical form the desired performance of the strategy illustrated in fig2 and a comparison thereof to performance without use of the strategy . the graph plots various vehicle performance values , such as engine 24 rotational velocity , generator motor 30 torque , and output shaft 44 torque , as a function of time for an event where a throttle is backed out from 30 % to 0 % and the transmission 60 up - shifts from a first gear to a second gear . a vertical axis 200 shows normalized values , ranging from zero ( 0 ) to one ( 1 ) for engine speed , generator motor 30 torque and output shaft 44 torque . a horizontal axis 202 represents time in seconds . engine speed plot lines 204 and 206 show engine 24 rotational velocities as a function of time . the engine speed plot line 204 shows engine 24 rotational velocity with the strategy shown in fig2 and described above activated . the engine speed plot line 206 shows engine 24 rotational velocities without the strategy . the engine speed plot lines 204 and 206 show engine 24 rotational velocities remain greater with the strategy active . a generator motor torque plot line 208 shows generator motor 30 torque as a function of time with the strategy shown in fig2 and described above activated . during the time period from about 0 . 8 second to about 1 . 1 seconds , the generator motor 30 applies alternating positive and negative torque to the system to maintain engine 24 rotational velocity , described above , and output shaft 44 torque , described below , at desired levels . output shaft torque plot lines 210 and 212 show output shaft 44 torque as a function of time . the output shaft torque plot line 210 shows output shaft 44 torque with the strategy shown in fig2 and described above activated . the output shaft torque plot line 212 shows output shaft 44 torques without the strategy . the output shaft torque plot lines 210 and 212 show , at about 0 . 9 seconds , an elimination of an undesirable negative torque spike when the strategy is active . the above - described embodiment of the invention is provided purely for purposes of example . many other variations , modifications , and applications of the invention may be made .