阅读说明：本技术 变矩器离合器打滑的模型预测控制 (Model predictive control of torque converter clutch slip ) 是由 J·C·萨瓦拉·朱雷多 G·西米尼 B·P·贾基洛 Z·张 Y-Y·王 H·阿特马拉姆 于 2020-01-17 设计创作，主要内容包括：一种用于控制变矩器离合器打滑的控制系统,包括：离合器设备模型,所述离合器设备模型被配置为预测与变矩器离合器打滑有关的参数值,所述参数值是包括命令离合器压力的离合器设备模型输入与来自扭矩产生装置的扭矩的函数。所述控制系统还包括模型预测控制器,所述模型预测控制器被配置为接收可确定与变矩器离合器打滑有关的期望参数值和与变矩器离合器打滑有关的预测参数值的信号,接收表示扭矩产生装置的报告扭矩的信号,识别导致基于所述离合器设备模型的目标函数的最佳值的最佳命令离合器压力值,和向致动器提供命令信号以有效地控制施加到所述变矩器离合器的命令离合器压力。(A control system for controlling torque converter clutch slip, comprising: a clutch device model configured to predict a parametric value related to torque converter clutch slip, the parametric value being a function of a clutch device model input comprising a commanded clutch pressure and torque from a torque-generative device. The control system further includes a model predictive controller configured to receive signals that determine a desired parametric value related to torque converter clutch slip and a predicted parametric value related to torque converter clutch slip, receive signals indicative of reported torque of the torque-generative device, identify an optimal commanded clutch pressure value that results in an optimal value based on an objective function of the clutch apparatus model, and provide a command signal to an actuator effective to control a commanded clutch pressure applied to the torque converter clutch.)

1. A control system that controls a slip of a torque converter clutch in a power transmission system including a torque generator and a torque converter including the torque converter clutch, wherein the control system comprises:

a clutch device model configured to predict a parametric value related to torque converter clutch slip, the parametric value being a function of a clutch device model input comprising a commanded clutch pressure and a torque from a torque-generative device; and

a model predictive controller configured to:

receiving signals capable of determining a desired parametric value related to torque converter clutch slip and a predicted parametric value related to torque converter clutch slip;

receiving a signal indicative of a reported torque of a torque-generative device;

identifying an optimal commanded clutch pressure value that results in an optimal value based on an objective function of the clutch device model; and

a command signal is provided to an actuator effective to control a command clutch pressure applied to the torque converter clutch.

2. The control system of claim 1, wherein the objective function includes a difference between a desired value of a parameter related to clutch slip and a predicted value of the parameter, a rate of change of clutch pressure, and a difference between a desired value and a predicted value of a commanded clutch pressure.

3. The control system of claim 2, wherein the objective function includes constraints on the commanded clutch pressure, the rate of change of the clutch pressure, and parameters related to clutch slip.

4. The control system of claim 2, wherein the model predictive controller receives inputs including a desired parameter value relating to clutch slip, a predicted parameter value relating to clutch slip, and torque from the torque-generative device.

5. The control system of claim 2, wherein the parameter related to clutch slip is clutch torque.

6. The control system of claim 5, wherein the clutch torque is calculated based in part on an estimated value of hydraulic torque transferred from an impeller to a turbine in the torque converter.

7. The control system of claim 6, wherein the estimate of hydraulic torque is calculated based on a k-factor.

8. The control system of claim 2, wherein the parameter related to clutch slip is clutch slip.

9. The control system of claim 8, wherein the clutch device model input further comprises an estimate of hydraulic torque transferred from a pump impeller to a turbine wheel in the torque converter.

10. The control system according to claim 9, wherein the hydraulic torque is estimated by a second order polynomial of slip.

Technical Field

The present invention relates to controlling slip in a Torque Converter Clutch (TCC), and more particularly to controlling TCC slip using Model Predictive Control (MPC).

Background

Torque converters are commonly used to transfer drive torque from a torque-generative device to a transmission. The torque converter can provide torque multiplication, smooth rate change during acceleration, and good torsional vibration damping. Because torque converters use fluid couplings between their input and output, fluid losses result in inherent inefficiencies. To achieve better fuel economy, automobile manufacturers use a lock-up clutch, known as a torque converter clutch or TCC, to mechanically lock the input to the output to reduce losses at steady state speed conditions. At lower gears and lower vehicle speeds, the TCC cannot be locked because the locked driveline can cause drivability problems. To strike a balance between vehicle drivability and fuel economy, systems have been developed that control the TCC to allow for a small rotational speed difference (also referred to as slip) between the torque converter input and output.

There is a need for improved TCC slip control to further improve vehicle drivability and fuel economy.

Disclosure of Invention

According to several aspects, there is provided a control system that controls a slip of a torque converter clutch in a power transmission system including a torque generating device and a torque converter including the torque converter clutch, the control system including: a clutch device model configured to predict a parametric value related to torque converter clutch slip, the parametric value being a function of a clutch device model input comprising a commanded clutch pressure and torque from the torque-generative device. The control system also includes a model predictive controller configured to receive signals from which a desired parametric value relating to torque converter clutch slip and a predicted parametric value relating to torque converter clutch slip may be determined. The model predictive controller is further configured to receive a signal indicative of a reported torque of a torque-generative device, identify an optimal commanded clutch pressure value resulting in an optimal value based on an objective function of the clutch apparatus model, and provide a command signal to an actuator effective to control a commanded clutch pressure applied to the torque converter clutch.

In another aspect of the disclosed control system, the objective function includes a difference between a desired value of a parameter related to clutch slip and a predicted value of the parameter, a rate of change of clutch pressure, and a difference between the desired value and a predicted value of a commanded clutch pressure.

In another aspect of the disclosed control system, the objective function includes constraints on commanded clutch pressure, rate of change of clutch pressure, and parameters related to clutch slip.

In another aspect of the disclosed control system, the model predictive controller receives inputs including a desired parameter value relating to clutch slip, a predicted parameter value relating to clutch slip, and torque from the torque-generative devices.

In another aspect of the disclosed control system, the parameter related to clutch slip is clutch torque.

In another aspect of the disclosed control system, the clutch torque is calculated based in part on an estimated value of hydraulic torque transmitted from an impeller to a turbine in the torque converter.

In another aspect of the disclosed control system, the estimate of hydraulic torque is calculated based on a k-factor.

In another aspect of the disclosed control system, the parameter related to clutch slip is clutch slip.

In another aspect of the disclosed control system, the clutch device model input further includes an estimated value of hydraulic torque transferred from an impeller to a turbine in the torque converter.

In another aspect of the disclosed control system, the hydraulic torque is estimated from a second order polynomial of slip.

According to several aspects, a method of controlling torque converter clutch slip in a powertrain system including a torque-generative device and a torque converter including a torque converter clutch is provided, the method comprising predicting a parametric value relating to torque converter clutch slip in a clutch device model, the parametric value being a function of a clutch device model input including a commanded clutch pressure and torque from the torque-generative device. The method further includes receiving signals in a model predictive controller that determine a desired parametric value related to torque converter clutch slip and a predicted parametric value related to torque converter clutch slip, receiving signals in the model predictive controller that represent reported torques of the torque-generative devices, identifying an optimal commanded clutch pressure value in the model predictive controller that results in an optimal value for the objective function being generated based on a model of the clutch apparatus; and providing a command signal to the actuator effective to control a commanded clutch pressure of the torque converter clutch.

In another aspect of the disclosed method, the objective function includes a difference between a desired value of a parameter related to clutch slip and a predicted value of the parameter, a rate of change of clutch pressure, and a difference between a desired value and a predicted value of a commanded clutch pressure.

In another aspect of the disclosed method, the objective function includes constraints on commanded clutch pressure, rate of change of clutch pressure, and parameters related to clutch slip.

In another aspect of the disclosed method, the model predictive controller receives inputs including a desired parameter value related to clutch slip, a predicted parameter value related to clutch slip, and torque from the torque-generative devices.

In another aspect of the disclosed method, the parameter related to clutch slip is clutch torque.

In another aspect of the disclosed method, the clutch torque is calculated based in part on an estimated value of hydraulic torque transmitted from an impeller to a turbine in a torque converter.

In another aspect of the disclosed method, the estimate of hydraulic torque is calculated based on a k-factor.

In another aspect of the disclosed method, the parameter related to clutch slip is clutch slip.

In another aspect of the disclosed method, the clutch device model input further includes an estimated value of hydraulic torque transferred from an impeller to a turbine in the torque converter.

According to several aspects, a system is provided that includes a torque converter including a torque converter clutch, a torque-generative device that provides torque to the torque converter, and an actuator that controls clutch pressure of the torque converter clutch. The system also includes a controller having a clutch apparatus model that predicts a parametric value related to torque converter clutch slip as a function of a clutch apparatus model input including a commanded clutch pressure and torque from the torque-generative device. The system further includes a model predictive controller that receives signals that determine a desired parametric value related to torque converter clutch slip and a predicted parametric value related to torque converter clutch slip, receives signals representing reported torques of the torque-generative devices, identifies an optimal commanded clutch pressure value that results in an optimal value based on an objective function of the clutch apparatus model, and provides a command signal to an actuator effective to provide the optimal commanded clutch pressure value applied to the torque converter clutch.

Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

Drawings

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

Embodiments of the invention will be described with reference to the accompanying drawings, in which:

FIG. 1 is a block diagram illustrating exemplary powertrain components of a vehicle;

FIG. 2 is a schematic illustration of an exemplary torque converter that may be included in the exemplary powertrain of FIG. 1;

FIG. 3 depicts elements of an exemplary torque converter identifying torque and inertia that affect dynamic behavior of the torque converter;

FIG. 4 is a block diagram schematically depicting an example MPC controller;

fig. 5 is a graph depicting the performance of the slip control system according to an exemplary embodiment.

Detailed Description

The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.

Referring now to the drawings, wherein the showings are for the purpose of illustrating certain exemplary embodiments only and not for the purpose of limiting the same, FIG. 1 is a block diagram of various powertrain components of a vehicle 10. The powertrain components include an engine 12 and a transmission 14. It should be understood that reference to "the engine 12" in this specification is for convenience and is not limited to an internal combustion engine. The teachings of the present invention may be applied to any torque-generative device 12, including, but not limited to, gasoline engines, diesel engines, and/or electric motors. An output shaft 16 of the engine 12 is coupled to an input of a torque converter 18 (i.e., an impeller or pump), and an input shaft 20 of the transmission 14 is coupled to an output of the torque converter 18 (i.e., a turbine). The torque converter 18 uses hydraulic fluid to transfer rotational energy from the engine 12 to the transmission 14 such that the engine 12 may be mechanically decoupled from the transmission 14 when necessary. The TCC22, which is actuated between a fully engaged position, a slip mode in which slip occurs, and a fully disengaged position, may apply TCC torque for controlling torque converter slip in the torque converter 18 between the engine 12 and the transmission 14. Engine output power 301 is depicted as engine speed ω_eAnd engine torque T_e. Likewise, transmission input power 303 is depicted as transmission input speed (which is equal to torque converter turbine speed ω)_t) And transmission input torque T_I(which is the TCC clutch torque T_CAnd torque converter torque T transmitted through the TCC turbine_hThe sum of). The slip in the torque converter 18 is defined as (ω)_e-ω_t). Of the change-speed gearing 14The output shaft 28 is coupled to a driveline 30 of the vehicle 10, which driveline 30 distributes engine power to the wheels in a manner well known to those of ordinary skill in the art. Transmission output power 305 is depicted as output speed N_OAnd output torque T_O。

The exemplary vehicle 10 also includes a controller 36, which is intended to represent an engine controller and a transmission controller; however, it should be understood that these two control functions may be served by a single device or by multiple communicatively connected devices. The controller 36 receives a throttle position signal from a vehicle throttle 38 and provides a signal to the engine 12 to produce the necessary engine speed and a signal to the transmission 14 to produce the necessary gear to meet the throttle demand. Additionally, the controller 36 provides a signal on line 40 to the TCC22 to control the actuation pressure P to achieve the desired torque converter slip. According to one exemplary method, the desired torque converter slip is a function of transmission gear state, engine torque, and turbine or input speed. In this context, the exemplary use of input speed is taken as an indirect measure of output speed or vehicle speed. The sensor 42 measures the output behavior of the transmission 14. In one exemplary embodiment, the sensor 42 measures the rotational speed of the output shaft 28 of the transmission 14 and sends a speed signal to the controller 36. Suitable non-limiting examples of the sensor 42 include an encoder or a speed sensor.

As noted above, the controller 36 may be a single device or a plurality of devices. Control module, controller, control unit, processor, and similar terms refer to any suitable combination or combinations of one or more of Application Specific Integrated Circuits (ASICs), electronic circuits, central processing units (preferably microprocessors), and associated memory and storage devices (read-only, programmable read-only, random access, hard disk drives, and the like) that execute one or more software or firmware programs, combinational logic circuits, input/output circuits and devices, suitable signal conditioning and buffer circuits, and other suitable components that provide the described functionality. The controller 36 has a set of control algorithms, including resident software program instructions and calibrations stored in memory and executed to provide the desired functions. The algorithm is preferably executed during a preset loop period. The algorithms are executed, such as by a central processing unit, and are operable to monitor inputs from sensing devices and other networked control modules, and execute control and diagnostic routines to control operation of actuators. The cycle period may be executed at regular intervals during ongoing engine and vehicle operation. Alternatively, the algorithms may be executed in response to occurrence of an event.

Referring now to FIG. 2, an exemplary torque converter 18 is illustrated that provides a fluid coupling between the engine 12 and the transmission 14. The torque converter 18 includes a housing 50, the housing 50 being fixed for rotation with the engine output shaft 16 (e.g., an engine crankshaft) via a flywheel 52. The impeller 54 is fixed for rotation with the housing 50 and the turbine 56 is fixed for rotation with the transmission input shaft 20. A stator 60 is also provided, and the stator 60 is fixed so as not to rotate. The interior of the torque converter 18 is filled with a viscous fluid. Rotation of the impeller 54 may cause corresponding viscous fluid movement that is directed through the stator 60 to the turbine 56 to induce rotation of the turbine 56. Although the coupling device 18 is described as a simplified torque converter, it should be appreciated that the coupling device 18 may take various other forms without departing from the scope of the present invention.

When the engine output shaft 16 rotates at idle speed, the pump impeller 54 is induced to rotate. However, idle speed is generally insufficient to overcome the braking force that prevents turbine 56 from rotating. As the braking force decreases or the engine speed increases, the pump impeller 54 drives the viscous fluid into the turbine runner 56 and induces the turbine runner 56 to rotate. Thus, drive torque is transferred from the engine output shaft 16 through the transmission 14 to propel the vehicle. Upon achieving a point where there is little or no RPM difference between the turbine 56 and the impeller 54, the TCC22 may be engaged to provide direct drive between the engine 12 and the transmission 14. Under such conditions, the impeller 54 is mechanically coupled to the turbine 56 such that the rotational speed of the turbine 56 is approximately equal to the speed of the engine output shaft 16.

A slip mode of the TCC22 is also provided. Slip is determined as the difference between the rotational speed of the engine output shaft 16 and the rotational speed of the transmission input shaft 20, wherein the transmission input shaft 20 is used to transmit power from the coupling device 18 to the transmission 14. The slip mode occurs by varying the clutch actuation pressure P supplied to the TCC22 by a hydraulic control system (not shown). The magnitude of the actuation pressure P is approximately maximum when the TCC22 is in the fully engaged position. As the actuation pressure P decreases, the TCC22 transitions from the fully engaged position to the fully disengaged position.

Torque converter slip may be controlled by applying TCC torque. The TCC includes structure that operates mechanically, electronically, or fluidly to controllably couple the impeller and turbine of the torque converter to regulate the allowable slip therebetween. When the TCC is fully released, the fluid interaction between the pump and turbine controls slip. The torque transmitted through the torque converter is either torque converter torque or turbine torque transmitted in the fluid interaction between the pump impeller and the turbine wheel. When the TCC is fully released, the TCC torque is substantially equal to zero. When the TCC is fully locked, there is likely to be no slip between the pump and turbine, and the TCC torque is equal to the torque transmitted through the torque converter. When the TCC is in the slip mode, the torque transmitted through the torque converter includes a portion of the torque that is TCC torque, and the remainder of the torque transmitted through the torque converter is turbine torque. In one exemplary control method, the pressure of hydraulic fluid to the TCC controls the force applied within the TCC and the TCC torque generated such that torque converter slip approaches a desired or reference slip value. By reducing the pressure of the hydraulic fluid to the torque converter clutch, torque converter slip for a given operating condition will increase. Similarly, by increasing the pressure of the hydraulic fluid to the torque converter clutch, torque converter slip for a given operating condition will be reduced.

Torque converter slip affects vehicle operation and drivability. Excessive slip at steady state reduces fuel efficiency; too little slip in the steady state may result in reduced drivability. Excessive or insufficient slip under transient conditions may result in an uncontrolled slip condition, resulting in a loss of power to the output, or a lock-up clutch or clutch "collapse" condition. As used herein, the term "TCC collapse" refers to a slip below the value calculated as (target slip minus offset value).

However, the expected slip in the transition may not be equal to the expected slip in the steady state condition. For example, during a commanded acceleration, slip can be increased to a controlled level, allowing the engine to rapidly accelerate and then decreased to rapidly increase output torque through the transmission. Setting such a desired slip value for TCC control may be described as selecting a reference slip.

Equations describing the dynamic behavior of the torque converter may be developed with reference to FIG. 3. The engine output shaft 16 is at an angular velocity ω_eAnd (4) rotating. Torque T_eIs the engine torque provided at the engine output shaft 16. Inertia Je represents rotational inertia of the engine crankshaft, and inertia Jtc represents rotational inertia of the torque converter pump side. The combined inertia Jt seen at the output shaft 16 is the sum of the engine crankshaft inertia Je and the torque converter inertia Jtc. The torque transferred to the transmission input shaft 20 is clutch torque T transferred by clutch 22_cAnd hydraulic torque T hydraulically transmitted from the impeller 54 to the turbine 56_hThe sum of (a) and (b).

In model predictive control, a discrete state space model is typically represented as:

x_k+1＝Ax_k+Bu_k

y_k＝Cx_k+Du_k

where x represents the model state matrix, y represents the model output matrix, u represents the model input matrix, and A, B, C and D are coefficient matrices.

Referring to FIG. 4, an example Model Predictive Control (MPC) controller 100 includes a plant model (plant model)102, control logic 104, and an observer 110. The control logic 104 provides a commanded control output signal 106 to the actual TCC 22. A signal 108 indicative of the actual operating condition of the TCC22 is provided to an observer 110. The observer 110 provides information 112 derived from the signal 108 to the control logic 104. With continued reference to fig. 4, an input signal 114 indicative of a desired operating point of the TCC is provided to the controller 104. The controller 104 accepts additional controller input signals 116 and the plant model 102 accepts additional plant input signals 118. The MPC controller 100 provides suggested control signals 120 to the plant model 102. The plant model 102 provides a predicted plant response 122 based on the proposed control signal 120 and the plant model input signals 118. The cost function is evaluated based on the desired operating point 114, the additional controller input signal 116, the predicted plant response 122, and the proposed control signal 120. The process is iterated to find the best suggested control signal 120 that minimizes the value of the cost function. The controller 104 then provides the optimized control signal to the actual TCC as the commanded control output signal 106. When the TCC responds to the new command control signal 106, the state of the system changes, and the controller 104 repeats the optimization process based on the state of the new system. Various embodiments described below may be implemented using an exemplary controller 100 as shown in fig. 4.

In the first exemplary embodiment, the device model 102 is a linear model of the TCC. In the present embodiment, the proposed control signal 120 is a proposed pressure command to the TCC model 102 and the predicted device response 122 is a predicted level of slip. An additional plant model input 118 is a reported engine torque signal, as reported by an Engine Control Module (ECM). The desired operating point 114 represents a desired level of TCC slip. The additional controller input signal 116 is representative of engine torque. The commanded control output signal 106 is a command pressure signal that is communicated to the actual TCC 22. Actual slip in the TCC22 is observed and provided as signal 112 to the controller 104.

For the first exemplary embodiment, the input terms and output terms in the discrete state space model may be represented as:

y＝s

wherein P is_TccIndicating TCC clutch activation pressure, T_eRepresenting engine torque and s representing TCC clutch slip.

For the first exemplary embodiment, exemplary cost functions may include slip error, rate of change of TCC input pressure, and TCC input reference pressure error integral. The cost function can be expressed as:

wherein:

subject to the constraints:

P_tcc,min,k≤P_tcc,k≤P_tcc,max,kk＝0,1,…,N-1

S_min,k+1≤s_k+1≤s_max,k+1k＝0,1,…,N-1

ΔP_tcc-min,k≤ΔP_tcc,k≤ΔP_tcc-max,kk＝0,1,…,N-1

the weighting factors for the cost function of the first exemplary embodiment include: w^slipWeighting factors for slip errors; w^ΔPtccA weighting factor for the rate of change of the input pressure; and W^PtccRefA weighting factor for the pressure reference error is input. The relative magnitudes of the various weighting factors of the cost function may be adjusted to facilitate different performance criteria. Examples of TCC performance criteria include, but are not limited to, slip errors (mean absolute, mean, standard deviation, maximum), undershoot or overshoot of slip errors, clutch energy, and avoiding TCC "collapse". As used herein, the term "TCC collapse" refers to a slip below the value calculated as (target slip minus offset value).

Fig. 5 shows a comparison of slip control results between a baseline PID (proportional-integral-derivative) slip control system and an MPC slip control system according to the first exemplary embodiment described herein. The graph in FIG. 5 represents the response of both control systems to a 15% throttle depression maneuver. Referring to fig. 5, a graph 150 is a plot with time in seconds represented on the x-axis and slip in rpm represented on the y-axis. In the graph 150, trace 156 represents the target TCC slip value as provided as input 114 in FIG. 4 for the first exemplary embodiment. Trace 154 represents the actual TCC slip value as provided in FIG. 4 as signal 112 for the first exemplary embodiment. The performance of the baseline PID slip control system undergoing the same 15% throttle depression maneuver is shown in FIG. 5 by trace 152. As shown in graph 150, the performance of the MPC system in accordance with the first exemplary embodiment is favorable compared to the performance of the baseline system, with a reduction in peak slip error of about 50%. With continued reference to FIG. 5, the graph 160 is a plot having time in seconds represented on the x-axis and pressure in kPa represented on the y-axis. In the graph 160, trace 162 represents the commanded TCC pressure, as provided to the TCC22 as input 106 in FIG. 4, which results in the slip shown in trace 154 in the graph 150. Trace 164 represents the commanded TCC pressure in the baseline PID system, which can result in the slip shown in trace 152 in graph 150. From the results in the graph 160, it can be appreciated that the MPC slip control system according to the first exemplary embodiment has a lower peak TCC pressure and a lower rate of change of TCC pressure than the baseline PID system.

In a second exemplary embodiment, referring again to FIG. 4, the device model 102 is a model of the TCC 22. In the present embodiment, the proposed control signal 120 is a proposed pressure command to the TCC model 102 and the predicted device response 122 is a predicted clutch torque. An additional plant model input 118 is a reported engine torque signal, as reported by an Engine Control Module (ECM). The desired operating point 114 represents a desired TCC clutch torque level. The additional controller input signal 116 is representative of engine torque. The commanded control output signal 106 is a command pressure signal that is communicated to the actual TCC 22. The estimated TCC clutch torque in TCC22 is calculated based on the engine torque and observed TCC slip and provided as signal 112 to controller 104.

Referring again to fig. 3, the angular acceleration of the engine output shaft 16 is given by:

using the k-factor torque converter model:

slip is defined as: s- ω_e-ω_tAnd the slip error is defined as: s_e＝s-s_d(ii) a Wherein s is_dIs the desired slip.

The time rate of change of slip error is given by:

solving for T_c：

In one aspect of the second embodiment, the clutch device model relates the clutch torque T_cWith engine torque T_eAnd commanded torque actuation pressure P_TccAnd (4) associating. In the following discussion, to simplify notation by reducing the number of subscript levels, the variable name CltTrq is used to represent the clutch torque T_c。

For this second exemplary embodiment, the input terms and output terms in the discrete state space model may be represented as:

u＝[P_Tcc]

y＝CltTrq

wherein P is_TccIndicates TCC clutch activation pressure and CltTrq indicates TCC clutch torque.

For this second exemplary embodiment, an exemplary cost function may include clutch torque error, rate of change of TCC input pressure, and TCC input reference pressure error integral. The cost function can be expressed as:

wherein:

subject to the constraints:

P_tcc,min,k≤P_tcc,k≤P_tcc,max,kk＝0,1,…,N-1

CltTrq_min,k+1≤CltTrq_k+1≤CltTrq_max,k+1k＝0,1,…,N-1

ΔP_tcc-min,k≤ΔP_tcc,k≤ΔP_tcc-max,kk＝0,1,…,N-1

the weighting factors for the cost function of the second exemplary embodiment include: w^CltTrqA weighting factor for the clutch torque error; w^ΔPtccA weighting factor for the rate of change of the input pressure; and W^PtccRefA weighting factor for the pressure reference error is input. The relative magnitudes of the various weighting factors of the cost function may be adjusted to facilitate different performance criteria. Examples of TCC performance criteria include, but are not limited to, slip errors (mean absolute, mean, standard deviation, maximum), undershoot or overshoot of slip errors, clutch energy, and avoiding TCC "collapse". As used herein, the term "TCC collapse" refers to a slip below the value calculated as (target slip minus offset value).

In a third exemplary embodiment, referring again to FIG. 4, the plant model 102 is a non-linear model of a TCC described by a linear system with non-linear disturbances including engine torque, non-linear portions of hydraulic torque, and shaft torsional vibrations. In one aspect of the third embodiment, the hydraulic torque in the operating range of interest is estimated by a second order polynomial of slip; i.e. T_h≈a(slip)+b(slip)². In the present embodiment, the proposed control signal 120 is a proposed pressure command to the TCC model 102 and the predicted device response 122 is a predicted level of slip. Additional plant model inputs 118 include reported engine torque signals, as reported by an Engine Control Module (ECM). Additional plant model inputs 118 also include hydraulic torque signals. The desired operating point 114 represents a desired level of TCC slip. The additional controller input signal 116 is representative of engine torque. The commanded control output signal 106 is a command pressure signal to the actual TCC 22. Actual slip in the TCC22 was observed and taken asSignal 112 is provided to controller 104.

For this third exemplary embodiment, the input terms and output terms in the discrete state space model may be represented as:

y＝s

wherein P is_TccIndicating TCC clutch activation pressure, T_eRepresenting engine torque, T_hHydraulic torque transmitted by the torque converter is indicated, and s indicates TCC clutch slip.

For this third exemplary embodiment, exemplary cost functions may include slip error, rate of change of TCC input pressure, and TCC input reference pressure error integral. The cost function can be expressed as:

wherein:

subject to the constraints:

P_tcc,min,k≤P_tcc,k≤P_tcc,max,kk＝0,1,…,N-1

s_min,k+1≤s_k+1≤s_max,k+1k＝0,1,…,N-1

ΔP_tcc-min,k≤ΔP_tcc,k≤ΔP_tcc-max,kk＝0,1,…,N-1

the weighting factors for the cost function of the first exemplary embodiment include: w^slipWeighting factors for slip errors; w^ΔPtccA weighting factor for the rate of change of the input pressure; and W^PtccRefA weighting factor for the pressure reference error is input. The relative magnitudes of the various weighting factors of the cost function may be adjusted to facilitate different performance criteria. Examples of TCC performance criteria include, but are not limited to, slip error (mean absolute, mean)Value, standard deviation, maximum), undershoot or overshoot of slip error, clutch energy, and avoiding TCC "collapse".

The control system of the present invention has several advantages. These advantages include improved slip control performance at operating points that are difficult to control using feedback and/or feedforward control systems. In addition, the control system of the present invention simplifies and reduces calibration effort and provides a systematic method of calibration. The control system according to the invention takes into account different target measures, such as slip error, rate of change of input pressure, etc., and allows weighting these measures to provide a desired driving experience based on the vehicle type. The control system of the invention is able to react to predicted disturbances.