METHOD FOR CONTROLLING A CONTINUOUSLY VARIABLE TRANSMISSION AND ASSOCIATED TRANSMISSION

Abstract

Method for controlling a continuously variable transmission (CVT) (140) in a powertrain system (100), the method comprising: determining a target clamping pressure (302) and an actual clamping pressure (304) for a clamping disc unit of the CVT (140); determining a proportional term (312) and an integral term (314) based on the target clamping pressure and the actual clamping pressure; determining a correction term for adjustment (327) via a control, based on the target clamping pressure (302) and a CVT temperature (306), wherein determining the correction term for adjustment (327) based on the target clamping pressure (302) and the CVT temperature (306) comprises selecting the correction term for adjustment (327) from a plurality of correction terms for adjustment (327) in a lookup table (600) stored in the cache memory (13) of the controller (12), wherein each of the many correction terms for adjustment is associated with a clamping pressure range (610) and a CVT temperature range (620), wherein the selected correction term for adjustment, which is associated in the lookup table (600) with the target clamping pressure (302) and CVT temperature (306), is updated based on the target clamping pressure (302) and the CVT temperature (306), wherein updating the selected correction term for adjustment (327) in the lookup table (600) is the updating of the includes selected correction terms for adjustment (327) in the lookup table (600),if the selected correction term for fitting (327) converges; , determining an assigned clamping pressure for the disc unit based on the proportional term (312), the integral term (314) and the adjustment term (327); regulating a final pressure command (335) via the control to drive an actuator (55, 65) of the movable disk (52, 64) of the clamping disk unit based on the instructed clamping pressure.

Description

TECHNICAL FIELD

[0001] This disclosure relates to a method for controlling a continuously variable transmission and an associated transmission. BACKGROUND

[0002] Internal combustion engine powertrains coupled with a continuously variable or infinitely variable transmission (CVT) can be used to provide traction power in vehicles. A CVT can operate with input / output ratios that are infinitely variable within a range between a minimum (underdrive) and a maximum (overdrive) ratio, thereby offering a choice of engine operation that allows a preferred balance of fuel consumption and engine performance in response to a driver's torque demand. The ability to provide continuously variable input / output ratios distinguishes a CVT from a stepped transmission, which has a variety of fixed ratios that can be selected incrementally in response to a torque demand.

[0003] Common chain-type CVT transmissions have two pulley units, each with two pulleys. A chain runs between the two pulley units, with the two pulleys of each pulley unit clamping the chain. The frictional engagement between the pulleys of each pulley unit and the chain couples the chain to each pulley unit, thus transferring torque from one pulley unit to the other. One pulley unit can act as the drive or input pulley unit, while the other can act as the driven or output pulley unit. The gear ratio is the ratio of the output pulley unit torque to the input pulley unit torque.The gear ratio can be changed by bringing the two conical pulleys of one unit closer together and the two conical pulleys of the other unit further apart, thereby pushing the chain ring on the respective unit further outwards or further inwards.

[0004] US 2015 / 0 148 158 A1 discloses a control device that controls a hydraulic pressure value output to an actuator based on a deviation of an actual flow from a target flow, which is calculated based on a target pressure, and using a proportional and an integral term as well as a fluid temperature. DE10047985A1 teaches a method for controlling an adjustment pressure using a PI controller, in which control parameters of the control device are adapted depending on the adjustment pressures to be set. EP 1 406 032 B1 discloses a hydraulic control device that calculates a line pressure based on the detection of a range selected by the operator and an oil temperature in order to achieve oil quantity compensation of an oil pump.DE 19940670 A1 relates to a system for controlling a hydraulic adjustment of the ratio of a continuously variable transmission, wherein the adjustment of the ratio is carried out by means of an electrical signal which is limited to maximum and minimum current values ​​based on the actual pressure. SUMMARY

[0005] An object underlying the invention is to provide an improved method for controlling a continuously variable transmission in a powertrain system and a corresponding transmission.

[0006] This object is achieved by the subject matter of the independent claims and in particular by the methods according to claims 1 and 5 and by a transmission according to claim 6.

[0007] A method for controlling a continuously variable transmission (CVT) is described, the method comprising: determining, via a controller, a desired clamping pressure for a pulley assembly to achieve a preferred gear ratio in the CVT in response to a torque request; determining, via a controller, an actual clamping pressure for the pulley assembly;determining an adjustment correction term based on the desired clamping pressure and a CVT temperature, wherein determining the adjustment correction term based on the desired clamping pressure and the CVT temperature comprises selecting the adjustment correction term from a plurality of adjustment correction terms in a lookup table stored in the cache memory of the controller, each of the plurality of adjustment correction terms associated with a clamping pressure range and a CVT temperature range, wherein the selected adjustment correction term associated with the desired clamping pressure and CVT temperature in the lookup table is updated based on the desired clamping pressure and the CVT temperature, wherein updating the selected adjustment correction term in the lookup table comprises updating the selected adjustment correction term in the lookup table when the selected adjustment correction term converges;determining a commanded clamping pressure for the clamping disc assembly based on the adjustment correction term; and regulating a pressure command via the controller to drive an actuator of the movable disc of the clamping disc assembly based on the commanded clamping pressure. A corresponding continuously variable transmission is also described.

[0008] The above features and advantages, as well as other features and advantages of the present teachings, will become apparent from the following detailed description of some of the best modes and other embodiments of the present teachings with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In the following, one or more embodiments are described by way of example with reference to the attached drawings, in which: Fig.1 schematically shows a drive system with an internal combustion engine rotatably connected to a continuously variable transmission (CVT) within the scope of the disclosure via a torque converter and a gearbox; Fig. 2 is a schematic cross-sectional illustration of the elements of a variator in a chain-type CVT in accordance with the disclosure; Fig. 3 is a schematic block diagram of a pressure control and error adjustment routine for controlling clamping pressure of a pulley assembly by a variator in one embodiment of the CVT and drive system in accordance with the disclosure with reference to Fig. 1 and Fig. 2; Fig.4 schematically shows the operation of a pressure control routine including the flow of the disc unit pressure control routine and the final disc unit clamping force control routine when the adjustment routine does not update one or more cells; Fig. 5 schematically shows an embodiment of a prediction routine for adaptation in accordance with the disclosure; and Fig. 6 schematically illustrates, in accordance with the disclosure, an example of the adjustment lookup table having a plurality of cells for storing adjustment correction terms, each cell corresponding to a pressure range for a pulley unit and a temperature range of the CVT. DETAILED DESCRIPTION

[0010] Referring to the drawings, in which the representations are for illustrating certain exemplary embodiments and not for the purpose of limiting the same, Fig. 1 schematically illustrates a drive system 100 including an internal combustion engine (motor) 110 rotatably connected to a continuously variable transmission (CVT) 140 via a torque converter 120 and a transmission housing 130. The drive system 100 is connected to a vehicle wheel 160 via a driveshaft 150 to provide traction power when used in a vehicle. The operation of the drive system 100 is regulated by a control system 10 in response to driver inputs and other factors.

[0011] The engine 110 may be any suitable internal combustion engine capable of converting fuel into mechanical energy to generate torque in response to demand from the control system 10. The torque converter 120 is a device having a fluid coupling between the input and output for transmitting torque and typically includes a pump 122 connected to the engine 110, a turbine 124 connected via an output member to the transmission housing 130, and a torque converter clutch 126 that connects the rotation of the pump 122 and the turbine 124 and is controlled by the control system 10. The output member of the torque converter 120 is rotatably connected to the transmission housing 130, where a gear set or other suitable gear mechanism acts as a reduction gear between the torque converter 120 and the CVT 140.Alternatively, the transmission housing 130 may include another suitable gear configuration to perform the transmission function between the engine 110, the torque converter 120, and the CVT 140, including, by way of non-limiting example, a chain ring gear or a planetary gear set. In alternative embodiments, the torque converter 120 and the transmission housing 130 may be omitted individually or together.

[0012] The transmission housing 130 includes an output member rotatably connected to the CVT 140 via an input member 51. An embodiment of the CVT 140 is described with reference to Fig.2. An output member 61 of the CVT 140 is rotatably connected to the input shaft 150, which in turn is rotatably connected to the vehicle wheels 160 via an axle, half shaft, or other suitable form of torque transmission. The drivetrain 150 may include a differential gear set, a chain and sprocket set, or other suitable transmission configuration for transmitting torque to one or more vehicle wheels 160.

[0013] The drive system 100 preferably includes one or more sensor devices for monitoring speeds of various devices, including, for example, an engine speed sensor 112, a torque converter turbine speed sensor 125, a CVT variator input speed sensor 32, a CVT variator output speed sensor 34, and a wheel speed sensor 162 for monitoring vehicle speed (Vss). Any suitable device capable of sensing rotational positions and speeds may be any of the aforementioned speed sensors, including, for example, a Hall-effect sensor. Each of the aforementioned speed sensors communicates with the control system 10.

[0014] The control system 10 preferably includes one or more control modules 12 and a user interface 14. For ease of illustration, a single controller 12 is shown. The controller 12 may include a plurality of control devices, with each of the controllers 12 dedicated to monitoring and controlling a single system. This may include an engine control module (ECM) for controlling the engine 110, a transmission control module (TCM) for controlling the CVT 140, and for monitoring and controlling a single subsystem, such as a torque converter clutch. The controller 12 preferably includes a storage device 11 with executable instruction sets and a cache memory 13. The user interface 14 communicates with user input devices, including, for example, an accelerator pedal 15, a brake pedal 16, and a gear selector 17.In one embodiment, the gear selector lever 17 has a tap-up / tap-down function for manually selecting a gear ratio and overriding the transmission control. An up tap command to the CVT 140 to increase the gear ratio is implemented by increasing the gear ratio on the variator. A down tap command to the CVT 140 to increase the gear ratio is implemented by increasing the gear ratio on the variator.

[0015] The terms controller, control module, module, controller, control unit, processor and the like refer to one or more combinations of application specific integrated circuit(s) (ASIC), electronic circuit(s), central processing unit(s) such as microprocessor(s) and associated non-volatile memory components in the form of storage and memory devices (read only memory, programmable read only memory, random access memory, hard disk, etc.) including cache memory 13. Cache memory 13 is preferably implemented as non-volatile memory with programmable read / write capabilities, which supports the storage of data arrays for retrieving power cycles such as those encountered in vehicles and key-off / key-on events.The non-volatile memory component may store machine-readable instructions in the form of one or more software or firmware programs, routines, combinational logic circuits, input / output circuits and devices, signal conditioning and buffer circuits, and other components accessible by one or more processors to provide described functionality. Input / output devices and circuits include analog-to-digital converter-related devices that monitor sensor inputs at a predetermined polling frequency or in response to a trigger event. Software, firmware, programs, instructions, control routines, code, algorithms, and similar terms refer to any set of instructions executable by a controller, such as calibrations and lookup tables.Each controller executes control routine(s) for the desired functions, including monitoring inputs from sensor devices and other networked controllers, and executing control and diagnostic routines to control the operation of actuators. The routines can be executed at regular intervals, such as every 100 microseconds during operation. Alternatively, routines can be executed in response to a trigger event. Communication between controllers and between controllers, actuators, and / or sensors can be established using a direct wired connection, a networked communication bus, a wireless connection, or another suitable communication link.Communication involves the exchange of data signals by any suitable means, including, as examples, electrical signals over a conductive medium, electromagnetic signals through air, optical signals over fiber optics, and the like. Data signals may include signals representing inputs from sensors and actuator commands, as well as communication signals between controllers. The term "model" refers to processor-based or processor-executable code and associated calibration used to simulate the physical existence of a device or physical process. As used herein, the term "dynamic" describes steps or processes that are executed in real time and are characterized by monitoring, otherwise determining, and periodically updating parameters during execution of a routine or between iterations of that execution.

[0016] Fig. Figure 2 schematically shows the elements of a variator 30 in a chain-type continuously variable transmission (CVT) 140, which can advantageously be controlled by the controller 12. The variator 30 transmits torque between the first rotating element 51 and the second rotating element 61. The first rotating element 51 is nominally referred to herein as the input member 51, and the second rotating element 61 as the output member 61.

[0017] The variator 30 includes a first, or primary, unit 36, a second, or secondary, unit 38, and a flexible, continuously rotatable device 40 connecting the first and second pulley units 36, 38 to transmit torque therebetween. The first pulley unit 36 ​​is rotatably mounted on the drive member 51, the second pulley unit 38 is rotatably mounted on the output member 61, and the rotatable device 40 is configured to transmit torque between the first and second pulley units 36, 38 and, thus, between the drive and output members 51, 61. The first pulley unit 36 ​​and drive member 51 rotate about a first axis 48, and the second pulley unit 38 and output member 61 rotate about a second axis 46.

[0018] The continuously rotatable device 40 may be a belt, a chain, or any other suitable, flexible, continuous device. The input speed sensor 32 may be mounted near the input link 51 and generates a value for the CVT input speed 33, which depends on the speed of the first pulley unit 36, and the output speed sensor 34 may be mounted near the output link 61 and generates a value for the CVT output speed 35, which depends on the speed of the second pulley unit 38. One of the pulley units 36, 38 functions as a ratio unit, establishing a speed ratio, and the other of the pulley units 36, 38 functions as a clamping unit, applying sufficient clamping force for torque transfer between the two. As used herein, the term 'speed ratio' refers to the speed ratio of the variator, which is a ratio between the CVT input speed and the CVT output speed.The CVT input speed can be determined from signal inputs from the engine speed sensor 112, the torque converter turbine speed sensor 125, or the input speed sensor 32 described herein, or from other suitable speed / position sensors. The CVT output speed can be determined from signal inputs from the output speed sensor 34 or the wheel speed sensor 162 described herein, or from other suitable speed / position sensors. The speed ratio parameters are determined based on the CVT input speed and the CVT output speed.

[0019] The first disk unit 36 ​​is divided perpendicular to the first rotation axis 48 into a first movable disk 52 and a first fixed disk 54, thus forming a first groove 50 between the two. The first movable disk 52 is moved or translated axially along the first axis 48 relative to the first fixed disk 54. For example, the first movable disk 52 can be connected to the drive member 51 by a spline, thus enabling the axial movement of the first movable disk 52 along the first axis 48. The first fixed disk 54 is mounted opposite the first movable disk 52. The first fixed disk 54 is axially fastened to the drive member 51 along the first axis 48. In this respect, the first fixed disk 54 is not movable in the axial direction of the first axis 48. The first movable disk 52 and the first fixed disk 54 each have a groove surface 56.The first surfaces 56 of the groove of the first movable disc 52 and the first fixed disc 54 face each other, thus forming the circular first groove 50 therebetween. The opposing surfaces 56 of the first groove preferably have the shape of an inverted truncated cone so that movement of the first movable disc 52 toward the first fixed disc 54 increases the outer diameter of the disc unit in the circular first groove 50. A first actuator 55 is arranged with the first disc unit 36 ​​so that it can regulate the axial position of the first movable disc 52 in response to a control signal 53, thereby moving the first movable disc 52 toward the first fixed disc 54. In one embodiment, the first actuator 55 is a hydraulically controlled device, and the control signal 53 is a hydraulic pressure signal.

[0020] The second disc unit 38 is split perpendicular to the second axis 46 to define a second circular groove 62. The second circular groove 62 is perpendicular to the second axis 46. The second disc unit 38 has a second movable disc 64 and a second fixed disc 66. The second movable disc 64 is moved or translated axially along the second axis 46 relative to the fixed disc 66. For example, the second movable disc 64 can be connected to the output member 61 by a spline, thus enabling the axial movement of the second movable disc 64 along the second axis 46. The second fixed disc 66 is mounted opposite the second movable disc 64. The second fixed disc 66 is axially attached to the output member 61 along the second axis 46. In this respect, the second fixed disc 66 is not movable in the axial direction of the second axis 46.The second movable disc 64 and the second fixed disc 66 each have a groove surface 68. The second groove surfaces 68 of the second movable disc 64 and the second fixed disc 66 face each other to form the circular second groove 62 therebetween. The opposing second groove surfaces 68 are preferably in the shape of an inverted truncated cone so that movement of the second movable disc 64 toward the second fixed disc 66 increases the outer diameter of the disc assembly in the circular second groove 62. A second actuator 65 is coupled to the second disc assembly 38 to regulate the axial position of the second movable disc 64 in response to a control signal 63, thereby moving the second movable disc 64 toward the second fixed disc 66.In one embodiment, the second actuator 65 is a hydraulically controlled device, and the control signal 63 is a hydraulic pressure signal. A ratio of the outer diameter of the first pulley assembly 36 to the outer diameter of the second pulley assembly 38 defines a transmission torque ratio. Other elements, such as clutch assemblies in the form of selectable one-way clutches and the like, can be installed between the variator 30 and other components of the drivetrain and drive system.

[0021] The variator speed ratio is a ratio of the speed of the input member 51 and the speed of the output member 61. An actual speed ratio is a present, measured value for the speed ratio and can be determined based on a ratio of the input speed signal 33 and the output speed signal 35. A desired speed ratio is a commanded, future value for the speed ratio determined based on monitored and estimated operating conditions related to an output power command, vehicle speed, engine torque, and other factors. The controller 12 utilizes control routines in controlling the CVT 140 to regulate the desired speed ratio by pressure control at one or both of the primary and secondary pulley assemblies 36 and 38 of the CVT 140.Pressure control for one or both of the primary and secondary pulley units of the CVT 140, 36 and 38, may be achieved by controlling the drive and actuating signals 53, 63 to apply the required pressure to the first and second actuators 55, 65 to change the desired speed ratio, preferably by providing the required pressures in the form of a primary and a secondary pressure command.

[0022] During operation, the clamping force of the disc unit must be sufficient to prevent chain slippage. To prevent chain slippage, a safety margin for a greater clamping force is added to the minimum clamping force of the disc unit. This requires higher fluid pressure, which is associated with increased pumping losses and impacts fuel consumption. In addition, errors can occur due to pressure variations between different vehicles. These can be caused by manufacturing changes, changes over time, and different operating conditions, such as the operating temperature of the CVT. Thus, a learning and adaptation procedure for errors due to pressure variation can minimize the need for larger initial clamping forces and increase control accuracy. The stability of the pressure control and the responsiveness of the transmission are influenced by pressure variation errors.

[0023] Fig.3 schematically shows a block diagram of a pressure control and fault adaptation routine (routine) 300 which determines the clamping force of the disc unit in an embodiment of the CVT 140 used in an embodiment of the drive system 100 with reference to the Fig. 1 and Fig.2 to improve the stability of the pressure control and the responsiveness of the CVT 140 to changes in output torque requests. Overall, the routine 300 includes a closed-loop pulley unit pressure control routine 310, an adjustment routine 320, and a final routine 330 that execute to determine a final clamping pressure command 335. The final clamping pressure command 335 is a pressure command to drive an actuator of a movable pulley of the first and second pulley units 36, 38 of the variator 30 of the CVT 140 based on the target pulley unit pressure 302 and the actual pulley unit pressure 304 inputs. As previously indicated, either the first or second pulley unit 36, 38 operates as a clamping unit.

[0024] The desired clamping pressure for the pulley assembly 302 is a clamping pressure of the pulley assembly to control the CVT 140 to a preferred operating point, such as a desired speed ratio, as part of the control of the powertrain system 100 to produce torque in response to a torque request, such as an operator input via the accelerator pedal 15 and / or the brake pedal 16. The actual pulley assembly pressure 304 is based on an input signal indicative of the actual pressure on the primary or secondary pulley assembly and may be based on a signal from a pressure sensor monitoring the pulley assembly pressure or other signals, such as the signals 33, 35 from the speed sensors 32, 34.

[0025] The pressure control routine 310 for the chain system creates a proportional pressure command 312 and an integral pressure command 314 based on the desired clamping pressure of the pulley unit 302 and the actual pressure of the pulley unit 304. The proportional pressure command 312 is preferably determined based on an arithmetic difference between the current desired clamping pressure of the pulley unit 302 and the current actual pressure of the pulley unit 304, which is multiplied by a scalar. The integral pressure command 314 is preferably determined based on differences between the desired clamping pressure of the pulley unit 302 and a corresponding actual pressure of the pulley unit 304 that have been accumulated over a period of time.

[0026] Fig.Figure 4 schematically illustrates the flow of a print control routine 400 in conjunction with the flow of routine 300, which executes the print control routine 310 for the chain system, and the final routine 330 in cases where the adjustment routine 320 does not update one or more cells. Table 1 is provided as a key, in which numerically labeled blocks and corresponding functions are set forth as follows. Table 1 BLOCK BLOCK CONTENT 402 Initiate the iteration; determine the proportional term, integral term and correction term for adaptation 404 Has the correction term been modified for adjustment in the lookup table? 406 Set the remaining integral of the fitting term equal to the difference between the integral term and change the correction term for fitting based on the modification 408 Set the reset value for the integral equal to the remaining integral term 410 Set the remaining integral term equal to the integral term for adjustment 412 Do you want an integral reset? 414 Set integral reset value equal to zero 416 Reset integral 418 Set the print command for the disk unit equal to the proportional term plus the remaining integral to adjust plus the correction term to adjust 420 End

[0027] The routine 400 runs periodically, at each iteration (402) a proportional term is determined, ie the proportional pressure command 312, an integral term, ie the integral pressure command 314, and a correction term for adjustment 327. An example of the lookup table for adjustments 600 is shown in Fig.6, including a plurality of cells having states for an adjustment correction term 327 that can be selected based on the commanded disc assembly pressure and the CVT temperature. The adjustment correction term 327 in each of the plurality of cells can be modified by the adjustment routine 320, as described herein. The routine 400 determines whether the adjustment correction term in the adjustment lookup table has been modified (404). If the adjustment correction term in the adjustment lookup table has been modified (404)(1), a remaining adjustment integral term is set equal to the difference between the integral term, i.e., the integral pressure command 314, and a change in the adjustment correction term by the modification (406), and an integral reset value is set equal to the remaining integral term (408).If the adjustment correction term in the adjustment lookup table has not been modified (404)(0), the remaining adjustment integral is set equal to the integral term, i.e., the integral pressure command 314 (410), and a determination is made as to whether there is a request or desire to reset the integral term (412). If there is (412)(1), an integral reset value is set to zero (414) and the integral term is reset (416). If there is no request or desire to reset the integral term (412)(0), or if the integral term has already been reset (416), the disk unit's pressure command, e.g., the final clamp pressure command 335, is set equal to a proportional term, e.g., the proportional pressure command 312 plus the remaining adjustment integral plus the adjustment correction term, e.g., the correction term 327.

[0028] Fig.6 schematically illustrates an example of the adjustment lookup table 600 having a plurality of cells 605 for storing the states for the adjustment correction term 327, each cell corresponding to a disk unit pressure range 610 on a horizontal axis and a CVT temperature range 620 on a vertical axis. The adjustment lookup table 600 may be stored as an array in the cache memory 13 of the controller 12. The disk unit 610 pressure ranges between a minimum disk unit pressure 611 and a maximum disk unit pressure 616 and is preferably divided into a plurality of pressure ranges. Five pressure ranges are shown, but the number of pressure ranges may be adjusted to any suitable amount. In one embodiment, the pressure ranges have equal sizes. In other embodiments, the individual pressure ranges may be different sizes.The CVT temperature 620 ranges between a minimum CVT temperature 621 and a maximum CVT temperature 629 and is preferably divided into a plurality of temperature ranges. Eight temperature ranges are shown between a minimum temperature, for example, -40°C, and a maximum temperature, for example, 150°C, but the number of temperature ranges can be adjusted to any suitable number. In one embodiment, the temperature ranges have equal sizes. In other embodiments, the individual temperature ranges can be different sizes. Cells 605 are each formed in the paired ranges of temperature 620 and pressure 610, and a state for the adjustment correction term 327 is stored in each of the cells 605. Under certain conditions, the adjustment routine 320 determines the adjustment correction term 327 based on the desired clamping pressure of the pulley assembly 302 and the CVT temperature 306.In such cases, the adaptation routine 320 takes a state for the adjustment correction term 327 from one of the cells 605 of the adaptation lookup table 600 based on the desired clamping pressure of the pulley assembly 302 and the CVT temperature 306 and uses it as described.

[0029] Under other conditions, the adaptation routine 320 modifies one or more of the conditions for the adaptation correction term 327 in one of the cells 605 of the adaptation lookup table 600 in response to an adaptation trigger signal 316 from an adaptation trigger routine 315. The adaptation trigger routine 315 may decide to modify one of the cells of the adaptation lookup table 600 based on the following factors: the proximity of the current operating conditions to cells in the adaptation lookup table 600, a calibrated trigger frequency, stability in the torque capacity ratio, the desired clamp pressure 302, the CVT temperature 306, stability in the desired clamp pressure, stability in the desired ratio, stability in the actual ratio, line pressure stability, clamp disk assembly status, operation in binary pump mode, and system diagnostics.

[0030] Again with reference to Fig.3, the adjustment routine 320 uses the proportional pressure command 312 and the integral pressure command 314 to determine and update the adjustment correction term 327. A remainder routine 328 determines a remaining pressure command 329 based on the difference between the adjustment correction term 327 and the integral pressure command 314. The final routine 330 combines the proportional pressure command 312, the adjustment correction term 327, and the remaining pressure command 329 to determine the final pressure command 335, the remaining pressure command 329 being provided as feedback to the first controller 310.

[0031] The adaptation routine 320 executes in response to the adaptation trigger signal 316 from the adaptation trigger routine 315 and includes an adaptation convergence routine 321, an adaptation prediction routine 322, a learning adaptation distribution term 324, and an adaptation lookup routine 326 for determining the adaptation correction term 327. The adaptation convergence routine 321 determines the cell convergence of one of the adaptation correction terms 327 stored in one of the cells 605 of the adaptation lookup table 600.Convergence of the adjustment correction term 327 stored in one of the targeted cells 605 may be achieved when both the target disc clamp pressure 302 and the CVT temperature 306 are within the calibrated limits for the target cell, the measured disc clamp pressure is within a calibrated tolerance of the target disc clamp pressure, and the closed loop proportional and integral terms remain below the calibrated limits for a calibrated period of time.

[0032] Fig.Figure 5 schematically illustrates one embodiment of the adjustment prediction routine 322. The adjustment prediction routine 322 executes to predict states of the adjustment correction term in neighboring cells in the adjustment lookup table 600 when the selected adjustment correction term converges in one of the cells of the adjustment lookup table 600. Cells in both directions of the axes within a calibrated range are candidates for adjustment prediction, with the axes including the disk unit pressure range 610 on the horizontal axis and the CVT temperature range 620 on the vertical axis, as shown. As such, the adjustment prediction routine 322 is a function of the convergence status of the surrounding cells. Table 2 is provided as a key, in which numerically labeled blocks and corresponding functions are set forth as follows. Table 2 BLOCK BLOCK CONTENT 500 Initiate adjustment prediction routine 502 Selected axis, direction of search: +X, -X, +Y, -Y from the newly converged cell 504 Is there a converged cell nearby? 506 Interpolate the non-converged cells between a newly converged cell and a converged cell nearby 508 Looking for forecast in all directions? 510 Application of the decay function to neighboring cells 512 Looking for forecast in all directions? 514 End

[0033] The fit prediction routine 322 runs when one of the cells of the fit lookup table 600 converges (500). The fit prediction routine 322 selects one of the axes and a direction for the search, for example, either positive (+) or negative (-) with respect to the newly converged cell (502). By way of example and with reference to Fig. 6, cell 631 may be a newly converged cell, and the axes may include the pressure range of disk unit 610 on the horizontal axis and the CVT temperature range 620 on the vertical axis. The search directions included increasing the pressure range of disk unit 610 (+X) 633, decreasing the pressure range of disk unit 610 (-X) 635, increasing the CVT temperature range 620 (+Y) 632, and decreasing the CVT temperature range (-Y) 634.

[0034] With further reference to Fig.5, the fit prediction routine 322 determines whether a previously converged cell is near the selected search direction (504)(1) and linearly interpolates between the newly converged cell and the previously converged cell in the vicinity to determine a predicted adjustment term 327 for all non-converged cells (506). The fit prediction routine 322 determines whether a search has made a prediction for both axes 610, 620 and both directions (+) and (-) (508), and if not (508)(0), the search continues (504); otherwise (508)(1), the search terminates (514).

[0035] By way of example and with reference to Fig.6, let cell 631 be a newly converged cell, cell 641 be a previously converged cell in the decreasing CVT temperature range (-Y) 634, and cell 643 be an intervening, non-converged cell. If cell 631 has a state of 100 and cell 641 has a state of 120, and cell 643 is a single intervening, non-converged cell, the adaptation prediction routine 322 assigns a state of (120 + 100) / 2 = 110 to cell 643 at 506.

[0036] Again with reference to Fig.5, when the adaptation prediction routine 322 determines whether a previously non-converged cell exists near the selected search direction (504)(0), a decay function is applied to the neighboring cells of the newly converged cell (508). In one embodiment, the decay function may be expressed as an array, for example, {75%, 25, 0%}, where the terms of the array are applied based on the proximity of the newly converged cell and an existing state of the cell in question. Thus, a cell with an existing state of zero adjacent to the newly converged cell is assigned a state 75% of the state of the newly converged cell, a cell one cell away from the newly converged cell is assigned a state 25% of the state of the newly converged cell, and a cell two cells away from the newly converged cell is assigned a state 0% of the state of the newly converged cell.Similarly, a cell with an existing state of M adjacent to the newly converged cell receives a state of 75% of the state of the newly converged cell plus 25% of the existing state M. A cell one cell away from the newly converged cell receives a state of 25% of the state of the newly converged cell plus 75% of the existing state M.

[0037] By way of example and with reference to Fig.6, cell 631 is the newly converged cell and there are no previously converged cells in the increasing pressure range of the disk unit 610 (+X) 633, in the decreasing pressure range of the disk unit 610 (-X) 635 or in the increasing CVT temperature range 620 (+Y) 632. If cell 631 has a newly assigned state 100, the cells 644, 645 adjacent to cell 631 with existing states zero are both assigned the state 75, the cell 648 adjacent to cell 631 with an existing state 20 is assigned a state ((75%*100) + (25%*20)) = 80 and cell 649 with an existing state 20 after removal from cell 631 is assigned a state ((25%*100) + (75%*20)) = 40.

[0038] Again with reference to Fig.5, the match prediction routine 322 determines whether a search has made a prediction for both axes 610, 620 and both directions (+) and (-) (512). If not (512)(0), the search continues (504); otherwise (512)(1), the search terminates (514). The match prediction routine 322 may also perform a search prediction to update the cell states of cells diagonal to the newly converged cell using similar methodologies as described herein.

[0039] Again with reference to Fig.3, the learning adaptation distribution term 324 is a modification of the proximity to breakpoint function of neighboring cells. This may include a surround gain search, where upper and lower levels of surround gains are established for each axis based on a relative proximity of the respective breakpoint. Each of the four neighboring adaptation cells calculates its individual surround gain as the product of the respective gain for each axis. The total desired adaptation modification is scaled for each cell by the respective surround gain. This scaled amount is then applied to the existing adaptation value without exceeding the total target learning error value.

[0040] Another approach for learning cells of the two-dimensional adaptation lookup table 600 involves modifying the pressure command to match the lookup table breakpoints. The modification occurs primarily for unconverged adaptation cells. Cell modification occurs only when the target clamp pressure and operating temperature are within calibrated limits for the adaptation cell in question. Preventing modification during deviating operating conditions preserves the adaptation integrity. Enabling modification of converged adaptation cells allows learning from any system pressure error over time. With each adaptation modification, each portion of the unadjusted integral shall be used in the next iteration of the loop. The full integral term is skipped during loop executions without modification of the adaptation table.

[0041] The final routine 330 combines the proportional pressure command 312, the adjustment correction term 327, and the remaining pressure command 329 to determine the final pressure command 335. The remaining pressure command 329 is provided as feedback to the first controller 310. The final pressure command 335 is executed by the first actuator 55 to control an axial position of the first movable discs 52 of the first disc unit 36 ​​in response to the drive signal 53, or alternatively, executed by the first actuator 55 to control an axial position of the second movable discs 64 of the second disc unit 38 in response to the drive signal 63.

[0042] The flowchart and block diagrams in the flowcharts illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present disclosure. In this regard, each block in the flowcharts or block diagrams may represent a module, segment, or portion of code that includes one or more of the executable instructions for implementing the specified logical function(s). It should also be understood that each block of the block diagrams and / or flowchart representations and combinations of blocks in the block diagrams and / or flowchart representations may be implemented by special-purpose hardware-based systems that perform the specified functions or operations, or combinations of special-purpose hardware and computer instructions.These computer program instructions may also be stored in a computer-readable medium that can direct a computer or other programmable data processing device to function in a particular manner such that the instructions stored in the computer-readable medium produce an article of manufacture, including instruction means for implementing the function or process depicted in the flowchart.

Claims

[1] A method for controlling a continuously variable transmission (CVT) (140) in a powertrain system (100), the method comprising: determining a target clamping pressure (302) and an actual clamping pressure (304) for a clamping disk unit of the CVT (140); determining a proportional term (312) and an integral term (314) based on the desired clamping pressure and the actual clamping pressure; determining a correction term for adaptation (327) via a controller based on the target clamping pressure (302) and a CVT temperature (306), wherein determining the adjustment correction term (327) based on the target clamping pressure (302) and the CVT temperature (306) comprises selecting the adjustment correction term (327) from a plurality of adjustment correction terms (327) in a lookup table (600) stored in the cache memory (13) of the controller (12), wherein each of the plurality of adjustment correction terms is associated with a clamping pressure range (610) and a CVT temperature range (620), wherein the selected adjustment correction term associated with the target clamping pressure (302) and CVT temperature (306) in the lookup table (600) is updated based on the target clamping pressure (302) and the CVT temperature (306), wherein updating the selected adjustment correction term (327) in the lookup table (600) Updating the selected correction term for adjustment (327) in the lookup table (600) includesif the selected correction term converges to the fit (327);, determining a commanded clamping pressure for the disc unit based on the proportional term (312), the integral term (314) and the adjustment correction term (327); regulating a final pressure command (335) via the controller to drive an actuator (55, 65) of the movable disc (52, 64) of the clamping disc unit based on the commanded clamping pressure. [2] The method of claim 1, wherein the selected adjustment correction term (327) converges when the actual clamp pressure (304) is within a calibrated range of the commanded clamp pressure and the proportional term (312) and the integral term (314) remain below the calibrated limit within a calibrated period of time. [3] The method of claim 1, further comprising predicting states of the adjustment correction terms (327) in adjacent cells in the lookup table (600) when the selected adjustment correction term (327) converges. [4] The method of claim 1, wherein the proportional term comprises a proportional pressure command (312) determined based on the arithmetic difference between the target clamping pressure (302) of the disc unit and the actual clamping pressure (304) of the disc unit. [5] A method for controlling a continuously variable transmission (CVT) (140), the method comprising: determining a desired clamping pressure (302) for a disc unit to achieve a preferred gear ratio in the CVT (140) in response to a torque request via a controller; determining an actual clamping pressure (304) for the disc unit; determining a correction term for adaptation (327) based on the target clamping pressure (302) and a CVT temperature (306), wherein determining the adjustment correction term (327) based on the target clamping pressure (302) and the CVT temperature (306) comprises selecting the adjustment correction term (327) from a plurality of adjustment correction terms (327) in a lookup table (600) stored in the cache memory (13) of the controller, wherein each of the plurality of adjustment correction terms (327) is associated with a clamping pressure range (610) and a CVT temperature range (620), wherein the selected adjustment correction term (327) associated with the target clamping pressure (302) and CVT temperature (306) in the lookup table (600) is updated based on the target clamping pressure (302) and the CVT temperature (306), wherein updating the selected adjustment correction term (327) in the lookup table (600) comprises updating the selected correction term for adjustment (327) in the lookup table (600),if the selected correction term converges to the fit (327);, determining a commanded clamping pressure for the clamping disc unit based on the correction term for adjustment (327); and regulating a final pressure command (335) via the controller to drive an actuator of the movable disc of the clamping disc unit based on the commanded clamping pressure. [6] Continuously variable transmission (CVT) (140), comprising: a variator having a first pulley unit (36) and a second pulley unit (38), the first and second pulley units (36, 38) rotatably coupled by a flexible continuously rotatable device (40), the first pulley unit (36) being rotatably coupled to an input member (51) and the second pulley unit (38) being rotatably coupled to an output member (61); the first disc unit (36) having a movable disc (52) that moves along a first axis (48) relative to a fixed disc (54) in response to the movement of a first actuator (55); the second disc unit (38) having a movable disc (64) that moves along a second axis (46) relative to a fixed disc (66) in response to the movement of a second actuator (65); a controller configured to communicate with a first sensor to monitor a first speed associated with the first disk unit (36) and a second sensor to monitor a second speed associated with the second disk unit (38), and operatively connected to the first (55) and second actuators (65); the control with an instruction set, the instruction set executable to: Determining a target clamping pressure (302) and an actual clamping pressure (304) for the first disc unit (36), wherein the first disc unit (36) acts as a clamping disc unit; Determining a proportional term (312) and an integral term (314) based on the desired clamping pressure (302) and the actual clamping pressure; Determining a correction term for adaptation (327) based on the target clamping pressure (302) and a CVT temperature (306), wherein determining the adjustment correction term (327) based on the target clamping pressure (302) and the CVT temperature (306) comprises selecting the adjustment correction term (327) from a plurality of adjustment correction terms (327) in a lookup table (600) stored in the cache memory (13) of the controller, wherein each of the plurality of adjustment correction terms (327) is associated with a clamping pressure range (610) and a CVT temperature range (620), wherein the selected adjustment correction term (327) associated with the target clamping pressure (302) and CVT temperature (306) in the lookup table (600) is updated based on the target clamping pressure (302) and the CVT temperature (306), wherein updating the selected adjustment correction term (327) in the lookup table (600) comprises updating the selected correction term for adjustment (327) in the lookup table (600),if the selected correction term converges to the fit (327);, Determining a commanded clamping pressure for the disc unit based on the proportional term, the integral term and the correction term for adjustment (327); and Controlling a final pressure command (335) for driving the first actuator (55) connected to the movable disc (52) of the first disc unit (36) based on the commanded clamping pressure. [7] The CVT of claim 6, wherein the controller instruction set selects the adjustment correction term (327) from a plurality of adjustment correction terms in a lookup table (600) stored in the cache memory (13) of the controller (12).

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