When an engagement-side clutch taking charge of rotation control in a downshift is the same as a rotation control clutch in the previous gear shift or a clutch of which the engagement has been switched in the previous gear shift, there is a likelihood that clutch hydraulic controllability will decrease and the clutch hydraulic controllability is secured by delaying start of the gear shift. It is possible to execute a gear shift which is a downshift without unnecessary waiting by setting a delay time by which the start of the gear shift is delayed depending on an accelerator depression amount such that the delay time is shorter when the accelerator depression amount is small than when the accelerator depression amount is large.

Methods and systems for a hydromechanical transmission. In one example, a vehicle system includes a hydromechanical transmission with a power-take off (PTO) that is designed to rotationally couple to an implement. The vehicle system further includes an engine coupled to the hydromechanical transmission and a power-management control unit configured to, during a drive or coast condition, cause the power-management control unit to: determine a net available power for the hydromechanical transmission and manage a power flow between the hydromechanical transmission, a drive axle, and the implement based on the net available power.

A control method is provided for a powertrain in a vehicle, the powertrain including an engine mechanically connected to a gearbox and an Electronic Control Unit (ECU), wherein the method includes allowing an extraordinary gear shift in spite of a first torque comparison indicating an expected engine output torque demand above a first general limit for allowed output torque associated with the extraordinary gear shift provided that: a second torque comparison indicates that the expected engine output torque demand after the extraordinary gear shift is within the limits of a second temporarily increased allowed engine output torque limit; and an extraordinary gear shift criteria is fulfilled indicating a gear shift is allowed the criteria being dependent on at least one parameter chosen among estimated fuel efficiency, engine efficiency, expected future torque demand, time of running the engine above the general engine torque limit and engine temperature.

A method of operating a transmission includes measuring an output torque, estimating a gearbox input torque using a model, and estimating gearbox component torques based on a detailed gearbox model. The model used to estimate the input torque varies depending on whether a torque converter is locked, open, or slipping. In some operating conditions, multiple estimates are available for gearbox input torque, impeller torque, or shift element torque in which case the models are adapted. When an estimated component torque is outside an expected range, a warning flag is raised and diagnostic data is saved. When an estimated torque approaches or exceeds a torque limit, the input torque command may be reduced to prevent component damage. A warning flag may also be raised and diagnostic data saved in response to a model parameter being adapted to a value outside of a predetermined range.

A method of protecting a frictional element of a clutch for an automatic transmission is provided. The method includes calculating an equivalent rotation number X of a frictional element using a trigonometric function equation on the basis of a virtual right triangle, by a control unit, if a rotation number of an engine exceeds a predetermined boundary value during a driving in a constant speed stage over a predetermined shift stage of an automatic transmission, entering a frictional element protection mode, by the control unit, if the control unit enters the frictional element protection mode, determining whether the calculated equivalent rotation number X of the frictional element exceeds a predetermined critical value, by the control unit, and if the equivalent rotation number X of the frictional element exceeds the predetermined critical value in a state in which the control unit enters the frictional element protection mode, reducing the rotation number of the engine by applying a target engine torque limiting value, by the control unit, the virtual right triangle being obtained using a rotation number Z of an output shaft, a rotation number Y of a turbine, and an equivalent rotation number X of the frictional element of the automatic transmission as a height, and using a number of teeth corresponding to the turbine, a number of teeth corresponding to the output shaft, and a virtual extension line as a base line.

A gear step estimation method is of estimating a gear step of a transmission device of an electric assist bicycle including a motor and the transmission device which is provided in a power transmission path between the motor and a rear wheel and is capable of switching the gear step among n gear steps. The gear step estimation method includes a step of acquiring, at a first time, a gear ratio that is a gear ratio of a transmission section that is the entire or partial power transmission path including the transmission device, a step of comparing the acquired gear ratio with n preset gear ratios set within a range of possible gear ratios taken by the n gear steps, and a step of estimating the gear step of the transmission device as an m-step in a case where the detected gear ratio matches an m-th preset gear ratios.