Method for managing lash in a driveline

Method for managing lash in a driveline operably coupled to a hybrid powertrain system, the hybrid powertrain system including an engine coupled to an input member of a hybrid transmission, the hybrid transmission operative to transmit torque between the input member and first and second torque machines and an output member coupled to the driveline to transmit torque to a wheel, the method comprising:

• monitoring an operator torque request;
• determining, in a control module, a net output torque command to the output member based upon the operator torque request;
• determining a change in a lash state comprising:
• comparing the net output torque command to a rate limit threshold torque comprising one of a positive rate limit threshold torque corresponding to a negative torque value and a negative rate limit threshold torque corresponding to a positive torque value, wherein the rate limit threshold torque is selected proximate to zero torque indicating potential lash in the transmission;
• and
• indicating the change in the lash state when the net output torque is one of less than the positive rate limit threshold and greater than the negative rate limit threshold;
• determining an output torque command comprising limiting the net output torque command by a threshold rate of change based upon the change in the lash state comprising one of:
• when the net output torque command is less than the positive rate limit threshold torque, limiting the output torque command based upon a maximum output torque decrease rate, and
• when the net output torque command is greater than the negative rate limit threshold torque, limiting the output torque command based upon a maximum output torque increase rate;
• and
• commanding motor torques to the first and second torque machines based upon the output torque command.

Method for managing lash in a driveline operably coupled to a hybrid powertrain system, the hybrid powertrain system including an engine, a second torque generating machine, a transmission device and an energy storage device connected to the second torque generating machine, the transmission device operative to transfer power between an output member, the engine and the second torque generating machine, the output member providing torque to the driveline providing torque to a wheel, the method comprising:

• monitoring an operator torque request;
• determining, in a control module, a net output torque command to the output member based upon the operator torque request;
• determining a change in a lash state comprising:
• comparing the net output torque command to a rate limit threshold torque comprising one of a positive rate limit threshold torque corresponding to a negative torque value and a negative rate limit threshold torque corresponding to a positive torque value, wherein the rate limit threshold torque is selected proximate to zero torque indicating potential lash in the transmission;
• and
• indicating the change in the lash state when the net output torque is one of less than the positive rate limit threshold and greater than the negative rate limit threshold;
• determining an output torque command comprising limiting the net output torque command by a threshold rate of change based upon the change in the lash state comprising one of:
• when the net output torque command is less than the positive rate limit threshold torque, limiting the output torque command based upon a maximum output torque decrease rate, and
• when the net output torque command is greater than the negative rate limit threshold torque, limiting the output torque command based upon a maximum output torque increase rate;
• and
• controlling the engine and the second torque generating machine based upon the output torque command.