Method and apparatus for controlling a multi-mode powertrain system

A method for controlling a powertrain system including an internal combustion engine coupled to a step-gear transmission that is operative in a plurality of transmission states, wherein the transmission may be commanded to execute a multi-state shift event, the method comprising:

• in response to a command to execute a multi-state shift event in the transmission in response to a command to accelerate, wherein the multi-state shift event includes sequentially executed transmission shifts to a plurality of transmission states, including an initial transmission state, a first intermediate transmission state, a second intermediate transmission state, and a final transmission state, wherein the first and second intermediate transmission states are selected to avoid transmission operation in a prohibited state during the shift event:
• prior to completion of a first state transition of the multi-state shift event that includes a commanded torque reduction during a transition from the initial transmission state to the intermediate transmission state:
• determining an initial maximum output torque limit,
• determining an initial commanded output torque based upon the initial maximum output torque limit, and
• controlling the internal combustion engine to generate torque in response to the initial commanded output torque;
• and
• after completion of the first state transition of the multi-state shift event, initiating operation in the first and second intermediate transmission states to effect the commanded torque reduction, including:
• determining a torque ramp rate based upon the initial maximum output torque limit,
• adjusting the initial commanded output torque based upon the torque ramp rate, and
• controlling the internal combustion engine to generate torque in response to the initial commanded output torque and the adjusted initial commanded output torque during a remainder of the multi-state shift event from the first intermediate transmission state to the second intermediate transmission state to the final transmission state.

A multi-mode powertrain system, comprising:

• an internal combustion engine and non-combustion torque machines configured to transfer torque to a transmission, wherein the transmission is operative in a plurality of transmission states;
• a controller operatively connected to the internal combustion engine, the non-combustion torque machines and the transmission, the controller including an instruction set, the instruction set executable to:
• command a multi-state transmission shift, wherein the multi-state shift event includes sequentially executed transmission shifts to multiple transmission states, including an initial transmission state, an intermediate transmission state, and a final transmission state, wherein the intermediate transmission state is selected to avoid transmission operation in a prohibited state during the shift event:
• prior to completion of a first state transition of the multi-state shift event that includes a commanded torque reduction during a transition from the initial transmission state to the intermediate transmission state:
• determine an initial maximum output torque limit,
• determine an initial commanded output torque based upon the initial maximum output torque limit and a plurality of torque constraints, and
• control the non-combustion torque machines to generate reactive torque in response to the initial commanded output torque;
• and
• after completion of the first state transition of the multi-state shift event, initiating operation in the intermediate transmission state to effect the commanded torque reduction, including:
• determine a torque ramp rate based upon the initial maximum output torque limit,
• adjust the initial commanded output torque based upon the torque ramp rate, and
• control the powertrain system to generate torque in response to the initial commanded output torque and the adjusted initial commanded output torque during a remainder of the multi-state shift event from the intermediate transmission state to the final transmission state.