Engagement control logic for an automatic transmission clutch with adaptive engagement feel

An electronic control system for controlling the engagement of a friction clutch of a multiple-ratio transmission in an automotive vehicle driveline during vehicle startup, the driveline having an output shaft and a throttle-controlled engine, the transmission having a torque converter with an impeller connected drivably to the engine and a turbine drivably connected to the friction clutch;

• the control system comprising a microprocessor including a calculation unit, a base control unit, memory storage registers and an adaptive control unit;
• a plurality of driveline sensors including an engine throttle position sensor, a transmission range selector position sensor, an output shaft speed sensor, a turbine speed sensor, and an engine speed sensor;
• the microprocessor having an input signal conditioner with signal flow paths for receiving input and feedbacks signals from the sensors including an engine speed signal, a turbine speed signal and an output shaft speed signal;
• the microprocessor further having a calculation unit for computing transmission input torque, friction clutch slip and vehicle speed based on the input and feedback signals, the microprocessor being characterized by sequential execution of software instructions in a continuous control loop in response to driveline input control data;
• the calculation unit detecting commanded slip rate of the friction clutch and comparing it to the actual slip rate to detect an error;
• a base control unit of the microprocessor receiving computed vehicle speed, slip rate error, transmission input torque and friction clutch slip and computing a friction clutch control signal whereby the friction torque capacity of the clutch is controlled;
• memory storage registers of the microprocessor including memory storage registers being in communication with the base control unit for storing clutch engagement parameters during each control loop of the microprocessor;
• the microprocessor including further an adaptative control unit for modifying the friction clutch engagement signal developed by the control unit during a current control loop of the microprocessor by adjusting clutch pressure values in accordance with control parameters stored in the memory storage registers during a preceding control loop thereby compensating driving friction clutch engagement for a base control unit of the microprocessor, the base control unit receiving computed vehicle speed, slip rate error, transmission input torque and friction clutch slip and computing a friction clutch control signal whereby the friction torque capacity of the clutch is controlled;
• the microprocessor adjusting clutch pressure values in accordance with control parameters stored in memory storage registers during the preceding control loop thereby compensating during friction clutch engagement for changes in system control parameters.

A method for controlling engagement of a pressure-operated friction clutch of a multiple-ratio automatic transmission in a vehicle driveline having a throttle-controlled engine and an output shaft, the method comprising:

• detecting driveline variables including throttle position, output shaft speed, engine speed, and transmission ratio;
• calculating control parameters including friction clutch slip, transmission input torque, commanded clutch slip rate, actual clutch slip rate, slip rate error, and vehicle speed as a function of the driveline control variables;
• determining desired clutch pressure as a function of current ratio, transmission input torque and vehicle speed;
• executing a friction clutch engagement cycle by initiating an engagement start mode wherein clutch pressure is commanded to effect incipient clutch engagement;
• initiating a torque transfer phase of the engagement cycle to control clutch pressure by increasing clutch pressure in the engagement start phase at a controlled rate;
• and
• initiating a slip change phase of the engagement cycle by controlling clutch pressure in a closed-loop fashion thereby decreasing clutch slip to a desired value over a predetermined time.

An electronic control system for controlling the engagement of a friction clutch of a multiple-ratio transmission in an automotive vehicle driveline during vehicle startup, the driveline having an output shaft and a throttle-controlled engine, the transmission having a torque converter with an impeller connected drivably to the engine and a turbine drivably connected to the friction clutch;

• the control system comprising a microprocessor including a calculation unit, a base control unit, memory storage registers and an adaptive control unit;
• a plurality of driveline sensors including an engine throttle position sensor, a transmission range selector position sensor, an output shaft speed sensor, a turbine speed sensor, and an engine speed sensor;
• the microprocessor having an input signal conditioner with signal flow paths for receiving input and feedbacks signals from the sensors including an engine speed signal, a turbine speed signal and an output shaft speed signal;
• the microprocessor further having a calculation unit for computing transmission input torque, friction clutch slip and vehicle speed based on the input and feedback signals, the microprocessor being characterized by sequential execution of software instructions in a continuous control loop in response to driveline input control data;
• the calculation unit detecting commanded slip rate of the friction clutch and comparing it to the actual slip rate to detect an error;
• and
• a base control unit of the microprocessor receiving computed vehicle speed, slip rate error, transmission input torque and friction clutch slip and computing a friction clutch control signal whereby the friction torque capacity of the clutch is controlled;
• memory storage registers of the microprocessor being in communication with the base control unit for storing clutch engagement parameters during each control loop of the microprocessor;
• the microprocessor including further an adaptative control unit for modifying the friction clutch engagement signal developed by the control unit during a current control loop of the microprocessor by adjusting clutch pressure values in accordance with control parameters stored in the memory storage registers during a preceding control loop thereby compensating driving friction clutch engagement;
• the microprocessor adjusting clutch pressure values in accordance with control parameters stored in memory storage registers during the preceding control loop thereby compensating during friction clutch engagement for changes in system control parameters;
• the transmission input torque calculated by the calculation unit being a feed-forward torque value, the calculation unit including a stored functional relationship between engine throttle position and engine torque and a torque multiplier value, the stored functional relationship being modified by the multiplier value to effect a torque product providing an early indication of friction clutch pressure requirements.

An electronic control system for controlling the engagement of a friction clutch of a multiple-ratio transmission in an automotive vehicle driveline during vehicle startup, the driveline having an output shaft and a throttle-controlled engine, the transmission having a torque converter with an impeller connected drivably to the engine and a turbine drivably connected to the friction clutch;

• the control system comprising a microprocessor including a calculation unit, a base control unit, memory storage registers and an adaptive control unit;
• a plurality of driveline sensors including an engine throttle position sensor, a transmission range selector position sensor, an output shaft speed sensor, a turbine speed sensor, and an engine speed sensor;
• the microprocessor having an input signal conditioner with signal flow paths for receiving input and feedbacks signals from the sensors including an engine speed signal, a turbine speed signal and an output shaft speed signal;
• the microprocessor further having a calculation unit for computing transmission input torque, friction clutch slip and vehicle speed based on the input and feedback signals, the microprocessor being characterized by sequential execution of software instructions in a continuous control loop in response to driveline input control data;
• the calculation unit detecting commanded slip rate of the friction clutch and comparing it to the actual slip rate to detect an error;
• and
• a base control unit of the microprocessor receiving computed vehicle speed, slip rate error, transmission input torque and friction clutch slip and computing a friction clutch control signal whereby the friction torque capacity of the clutch is controlled;
• memory storage registers of the microprocessor being in communication with the base control unit for storing clutch engagement parameters during each control loop of the microprocessor;
• the microprocessor including further an adaptative control unit for modifying the friction clutch engagement signal developed by the control unit during a current control loop of the microprocessor by adjusting clutch pressure values in accordance with control parameters stored in the memory storage registers during a preceding control loop thereby compensating driving friction clutch engagement;
• the engine speed sensor, the turbine speed sensor and the output shaft speed sensor communicating with the calculation unit in a closed-loop fashion whereby the calculation unit determines in real time output signals indicating a vehicle speed signal, a clutch slip signal and commanded and actual friction clutch slip rate signals, output signals of the calculation unit being communicated to the base control unit;
• the transmission input torque calculated by the calculation unit being a feed-forward torque value, the calculation unit including a stored functional relationship between engine throttle position and engine torque and a torque multiplier value, the stored functional relationship being modified by the multiplier value to effect a torque product providing an early indication of friction clutch pressure requirements.

A method for controlling engagement of a pressure-operated friction clutch of a multiple-ratio automatic transmission in a vehicle driveline having a throttle-controlled engine and an output shaft, the method comprising:

• detecting driveline variables including throttle position, output shaft speed, engine speed, and transmission ratio;
• calculating control parameters including friction clutch slip, transmission input torque, commanded clutch slip rate, actual clutch slip rate, slip rate error, and vehicle speed as a function of the driveline control variables;
• determining desired clutch pressure as a function of current ratio, transmission input torque and vehicle speed;
• executing a friction clutch engagement cycle by initiating an engagement start mode wherein clutch pressure is commanded to effect incipient clutch engagement;
• initiating a torque transfer phase of the engagement cycle to control clutch pressure by increasing clutch pressure in the engagement start phase at a controlled rate;
• and
• initiating a slip change phase of the engagement cycle by controlling clutch pressure in a closed-loop fashion thereby decreasing clutch slip to a desired value over a predetermined time;
• the step of increasing clutch pressure at a controlled rate being achieved by increasing commanded clutch pressure as follows:
• PR_CMDoc={PR_CMDoc_old+PRSLTT+ΔTQ_trans*MLTQoc/GAINoc}*MLTEoc
• where
• PRSLTT=slope of the pressure increase
• ΔTQ_trans=change in transmission input torque from previous loop
• and where
• PR_CMDoc=PR_CMDoc=[{TQ_TRANS+TQ_iα,}* MLTQoc/GAINoc+PRSToc−Cfoc*(NT/1000)2+FNpnPRTTOF(TP)−PRDL_rom+PRDL_kam]*MLTEoc
• where
• PR_CMDoc = Oncoming clutch commanded pressure TQ_TRANS = Input torque to transmission (computed as a torque-feed-forward by the engine controller, not shown) Cfoc = Conversion constant for centrifugal force compensation TQ_iα = Inertial torque based on inertia, change in turbine speed, and desired ratio change time { = CONST * Inertia * ΔNT/ratio change time} MLTQoc = Ratio of clutch torque to input torque MLTEoc = Temperature compensation multiplier GAINoc = Clutch gain PRSToc = Oncoming clutch stroke pressure NT = Turbine speed PRDL_rom = Delta clutch pressure from ROM table PRDL_kam = Delta clutch pressure from KAM table FNpnPRTTOF(TP) = Increment in commanded pressure for faster response.

A method for controlling engagement of a pressure-operated friction clutch of a multiple-ratio automatic transmission in a vehicle driveline having a throttle-controlled engine and an output shaft, the method comprising:

• detecting driveline variables including throttle position, output shaft speed, engine speed, and transmission ratio;
• calculating control parameters including friction clutch slip, transmission input torque, commanded clutch slip rate, actual clutch slip rate, slip rate error, and vehicle speed as a function of the driveline control variables;
• determining desired clutch pressure as a function of current ratio, transmission input torque and vehicle speed;
• executing a friction clutch engagement cycle by initiating an engagement start mode wherein clutch pressure is commanded to effect incipient clutch engagement;
• initiating a torque transfer phase of the engagement cycle to control clutch pressure by increasing clutch pressure in the engagement start phase at a controlled rate;
• and
• initiating a slip change phase of the engagement cycle by controlling clutch pressure in a closed-loop fashion thereby decreasing clutch slip to a desired value over a predetermined time;
• the slip change phase being followed during the engagement cycle by an engagement end phase whereby the commanded clutch pressure is increased nonlinearly until it reaches the commanded pressure thereby effecting full clutch engagement without an inertia torque disturbance during the engagement cycle;
• and
• the closed-loop clutch control in the slip change phase of the engagement cycle being achieved by increasing commanded pressure for the clutch as follows:
• PR_CMDoc=[PR_CMDoc_old+ΔP(PID)*FNFRRB(ctr_ramp)+FNPRCO(ΔTP)+CCPRTF*(ΔTQ_TRANS)]*FNMLTEoc(tempr.)
• where:
• FNFRRB(ctr_ramp) is a multiplier as a function of loop count from the start of ratio change to reduce the gain of PID controller for the first few loops, for smooth transition;
• FNPRCO(ΔTP) is a feed-forward term to compensate for sudden large changes in throttle position (ahead of torque changes);
• CCPRTF is a constant torque feed-forward term to compensate for changes in input torque;
• and
• FNMLTEoc(tempr.) is a temperature compensation multiplier;
• and where:
• ΔP(PID)=Kc*[Kp*(SLR_ERR_TO-SLR_ERR_T1)+Ki*SLR_ERR_TO+Kd* (SLR_ERR_TO−2*SLR_ERR_T1+SLR_ERR_T2)],
• where:
• SLR_ERR is computed as the difference between commanded and actual slip rates;
• SLR_ERR_TO, SLR_ERR_T1, SLR_ERR_T2 are control errors at current loop, previous loop, and one loop before previous loop, respectively;
• Kc is the overall gain, Kp is the proportional gain, Ki is the integral gain, and Kd is the derivative gain.