VARIABLE TRANSMISSION

RELATED APPLICATIONS

The present application claims the benefit of U.S. Provisional Application No. 62/441,721 and U.S. Provisional Application No. 62/441,731, each filed on January 3, 2017, which are incorporated herein by reference in their entirety.

BACKGROUND

Continuously variable transmissions (CVT) and transmissions that are substantially continuously variable are increasingly gaining acceptance in various applications. The process of controlling the ratio provided by the CVT is complicated by the continuously variable or minute gradations in ratio presented by the CVT.

Furthermore, the range of ratios that are available to be implemented in a CVT are not sufficient for some applications. A transmission is capable of implementing a combination of a CVT with one or more additional CVT stages, one or more fixed ratio range splitters, or some combination thereof in order to extend the range of available ratios. The combination of a CVT with one or more additional stages further complicates the ratio control process, as the transmission will have multiple

configurations that achieve the same final drive ratio.

The different transmission configurations can for example, multiply input torque across the different transmission stages in different manners to achieve the same final drive ratio. However, some configurations provide more flexibility or better efficiency than other configurations providing the same final drive ratio.

SUMMARY

Provided herein is a method for controlling a continuously variable drive (CVD) having a ball-planetary variator (CVP) provided with a ball in contact with a first traction ring assembly, a second traction ring assembly, and an idler assembly, wherein the CVP is operably coupled to a multiple speed gear box, the method including the steps of: receiving a plurality of input signals indicative of an input shaft speed, an output shaft speed, and a first traction ring speed; evaluating a second traction ring speed; determining a CVP speed ratio and a CVD speed ratio, wherein the CVP speed ratio is indicative of the speed ratio through the CVP, and wherein the CVD speed ratio is indicative of the speed ratio through the CVD; determining an error in the CVP speed ratio; determining an error in the CVD speed ratio; and issuing a plurality of fault conditions based at least in part on the CVP speed ratio error and the CVD speed ratio error.

Provided herein is a vehicle including: a continuously variable drive (CVD) including: a first rotatable shaft operably coupleable to a source of rotational power, the first rotatable shaft forming a main axis; a continuously variable planetary (CVP), wherein the CVP is a ball variator assembly having a first traction ring assembly and a second traction ring assembly in contact with a plurality of balls, wherein each ball of the plurality of balls has a tiltable axis of rotation and wherein the ball variator assembly is coaxial with the main axis; a CVD input planetary gear set having a ring gear, a planet carrier, and a sun gear, wherein the planet carrier is operably coupled to the first rotatable shaft, the ring gear is coupled to the first traction ring assembly, and the sun gear is coupled to the second traction ring assembly; a multiple speed gearbox having a number of selectable speed ranges, wherein the multiple speed gearbox is operably coupled to the second traction ring assembly and the sun gear; and a controller configured to identify a plurality of fault conditions of the CVD, the fault conditions including: a CVD input planetary damage fault; a CVP small slip fault; and a CVP gross slip fault.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

Novel features of the preferred embodiments are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present embodiments will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the devices are utilized, and the accompanying drawings of which:

Figure 1 is a side sectional view of a ball-type variator.

Figure 2 is a plan view of a carrier member that used in the variator of Figure 1. Figure 3 is an illustrative view of different tilt positions of the ball-type variator of Figure 1.

Figure 4 is a block diagram schematic of a vehicle control system that is implementable in a vehicle.

Figure 5 is a schematic diagram of an exemplary continuously variable drive configured to be controlled by the vehicle control system of Figure 4.

Figure 6 is a table depicting the operating modes of the continuously variable drive of Figure 5.

Figure 7 is a flow chart depicting a slip diagnostic process that is implementable in the vehicle control system of Figure 4.

Figure 8 is a schematic diagram of an exemplary configuration of a CVP with a lock-up clutch.

Figure 9 is a table depicting a number of fault conditions identified in the slip diagnostic process of Figure 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An electronic controller is described herein that enables electronic control over a variable ratio transmission having a continuously variable ratio portion, such as a Continuously Variable Transmission (CVT), Infinitely Variable Transmission (IVT), or variator. The electronic controller is configured to receive input signals indicative of parameters associated with an engine coupled to the transmission. The parameters can include throttle position sensor values, accelerator pedal position sensor values, vehicle speed, gear selector position, user-selectable mode configurations, and the like, or some combination thereof. The electronic controller can also receive one or more control inputs. The electronic controller can determine an active range and an active variator mode based on the input signals and control inputs. The electronic controller can control a final drive ratio of the variable ratio transmission by controlling one or more electronic actuators and/or solenoids that control the ratios of one or more portions of the variable ratio transmission.

The electronic controller described herein is described in the context of a continuous variable transmission, such as the continuous variable transmission of the type described in U.S. Patent Application Number 14/425,842, entitled "3-Mode Front Wheel Drive And Rear Wheel Drive Continuously Variable Planetary Transmission" and, U.S. Patent Application Number 15/572,288, entitled "Control Method of Synchronous Shifting of a Multi-Range Transmission Comprising a Continuously Variable Planetary Mechanism", each assigned to the assignee of the present application and hereby incorporated by reference herein in its entirety. However, the electronic controller is not limited to controlling a particular type of transmission but rather, is optionally configured to control any of several types of variable ratio transmissions.

Provided herein are configurations of CVTs based on a ball-type variator, also known as CVP, for continuously variable planetary. Basic concepts of a ball-type Continuously Variable Transmissions are described in United States Patent No.

8,469,856 and 8,870,711 incorporated herein by reference in their entirety. Such a CVT, adapted herein as described throughout this specification, includes a number of balls (planets, spheres) 1, depending on the application, two ring (disc) assemblies with a conical surface contact with the balls, as input (first) traction ring assembly 2 and output (second) traction ring assembly 3, and an idler (sun) assembly 4 as shown on FIG. 1. In some embodiments, the output traction ring assembly 3 includes an axial force generator mechanism. The balls are mounted on tiltable axles 5, themselves held in a carrier (stator, cage) assembly having a first carrier member 6 operably coupled to a second carrier member 7. The first carrier member 6 rotates with respect to the second carrier member 7, and vice versa. In some embodiments, the first carrier member 6 is substantially fixed from rotation while the second carrier member 7 is configured to rotate with respect to the first carrier member, and vice versa. In one embodiment, the first carrier member 6 is provided with a number of radial guide slots

8. The second carrier member 7 is provided with a number of radially offset guide slots

9, as illustrated in FIG. 2. The radial guide slots 8 and the radially offset guide slots 9 are adapted to guide the tiltable axles 5. The axles 5 are adjustable to achieve a desired ratio of input speed to output speed during operation of the CVT. In some

embodiments, adjustment of the axles 5 involves control of the position of the first and second carrier members to impart a tilting of the axles 5 and thereby adjusts the speed ratio of the variator. Other types of ball CVTs also exist, like the one produced by Milner, but are slightly different.

The working principle of such a CVP of FIG. 1 is shown on FIG. 3. The CVP itself works with a traction fluid. The lubricant between the ball and the conical rings acts as a solid at high pressure, transferring the power from the input ring, through the balls, to the output ring. By tilting the balls' axes, the ratio is changed between input and output. When the axis is horizontal, the ratio is one, as illustrated in FIG. 3, when the axis is tilted, the distance between the axis and the contact point change, modifying the overall ratio. All the balls' axes are tilted at the same time with a mechanism included in the carrier and/or idler. Embodiments disclosed herein are related to the control of a variator and/or a CVT using generally spherical planets each having a tiltable axis of rotation that is adjustable to achieve a desired ratio of input speed to output speed during operation. In some embodiments, adjustment of said axis of rotation involves angular misalignment of the planet axis in a first plane in order to achieve an angular adjustment of the planet axis in a second plane that is substantially perpendicular to the first plane, thereby adjusting the speed ratio of the variator. The angular misalignment in the first plane is referred to here as "skew", "skew angle", and/or "skew condition". In one embodiment, a control system coordinates the use of a skew angle to generate forces between certain contacting components in the variator that will tilt the planet axis of rotation. The tilting of the planet axis of rotation adjusts the speed ratio of the variator.

As used here, the terms "operationally connected," "operationally coupled", "operationally linked", "operably connected", "operably coupled", "operably coupleable", "operably linked," and like terms, refer to a relationship (mechanical, linkage, coupling, etc.) between elements whereby operation of one element results in a corresponding, following, or simultaneous operation or actuation of a second element. It is noted that in using said terms to describe the embodiments, specific structures or mechanisms that link or couple the elements are typically described. However, unless otherwise specifically stated, when one of said terms is used, the term indicates that the actual linkage or coupling will take a variety of forms, which in certain instances will be readily apparent to a person of ordinary skill in the relevant technology.

For description purposes, the term "radial", as used herein indicates a direction or position that is perpendicular relative to a longitudinal axis of a transmission or variator. The term "axial" as used herein refers to a direction or position along an axis that is parallel to a main or longitudinal axis of a transmission or variator.

It should be noted that reference herein to "traction" does not exclude applications where the dominant or exclusive mode of power transfer is through "friction." Without attempting to establish a categorical difference between traction and friction drives herein, generally, these are understood as different regimes of power transfer. Traction drives usually involve the transfer of power between two elements by shear forces in a thin fluid layer trapped between the elements. The fluids used in these applications usually exhibit traction coefficients greater than conventional mineral oils. The traction coefficient (μ) represents the maximum available traction forces that would be available at the interfaces of the contacting components and is a measure of the maximum available drive torque. Typically, friction drives generally relate to transferring power between two elements by frictional forces between the elements. For the purposes of this disclosure, it should be understood that the CVTs described here can operate in both tractive and frictional applications. As a general matter, the traction coefficient μ is a function of the traction fluid properties, the nonnal force at the contact area, and the velocity of the traction fluid in the contact area, among other things. For a given traction fluid, the traction coefficient μ increases with increasing relative velocities of components, until the traction coefficient μ reaches a maximum capacity after which the traction coefficient μ decays. The condition of exceeding the maximum capacity of the traction fluid is often referred to as "gross slip condition". Traction fluid is also influenced by entrainment speed of the fluid and temperature at the contact patch, for example, the traction coefficient is generally highest near zero speed and decays as a weak function of speed. The traction coefficient often improves with increasing temperature until a point at which the traction coefficient rapidly degrades.

As used herein, "creep", "ratio droop", or "slip" is the discrete local motion of a body relative to another and is exemplified by the relative velocities of rolling contact components such as the mechanism described herein. In traction drives, the transfer of power from a driving element to a driven element via a traction interface requires creep. Usually, creep in the direction of power transfer, is referred to as "creep in the rolling direction." Sometimes the driving and driven elements experience creep in a direction orthogonal to the power transfer direction, in such a case this component of creep is referred to as "transverse creep." Those of skill will recognize that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein, including with reference to the transmission control system described herein, for example, can be implemented as electronic hardware, software stored on a computer readable medium and executable by a processor, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described herein generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans can implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present embodiments. For example, various illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein can be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor can be a microprocessor, but in the alternative, the processor can be any conventional processor, controller, microcontroller, or state machine. A processor can also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of

microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. Software associated with such modules can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other suitable form of storage medium known in the art. An exemplary storage medium is coupled to the processor such the processor reads information from, and write information to, the storage medium. In the alternative, the storage medium can be integral to the processor. The processor and the storage medium can reside in an ASIC. For example, in one embodiment, a controller for use of control of the CVT includes a processor (not shown).

Referring now to FIG. 4, in some embodiments, a vehicle control system 100 includes an input signal processing module 102, a transmission control module 104 and an output signal processing module 106. The input signal processing module 102 is configured to receive a number of electronic signals from sensors provided on the vehicle and/or transmission. The sensors optionally include temperature sensors, speed sensors, position sensors, among others. In some embodiments, the signal processing module 102 optionally includes various sub-modules to perform routines such as signal acquisition, signal arbitration, or other known methods for signal processing. The output signal processing module 106 is optionally configured to electronically communicate to a variety of actuators and sensors. In some embodiments, the output signal processing module 106 is configured to transmit commanded signals to actuators based on target values determined in the transmission control module 104. The transmission control module 104 optionally includes a variety of sub-modules or subroutines for controlling continuously variable transmissions of the type discussed here. For example, the transmission control module 104 optionally includes a clutch control sub-module 108 that is programmed to execute control over clutches or similar devices within the transmission. In some embodiments, the clutch control sub-module implements state machine control for the coordination of engagement of clutches or similar devices. The transmission control module 104 optionally includes a CVP control sub-module 110 programmed to execute a variety of measurements and determine target operating conditions of the CVP, for example, of the ball-type continuously variable transmissions discussed here. It should be noted that the CVP control sub-module 110 optionally incorporates a number of sub-modules for performing measurements and control of the CVP. In some embodiments, the vehicle control system 100 includes an engine control module 112 configured to receive signals from the input signal processing module 102 and in communication with the output signal processing module 106. The engine control module 112 is configured to communicate with the transmission control module 104.

Referring now to FIG. 5, control and diagnostic methods described herein are related to continuously variable drives having a multiple speed gear box operably coupled to a continuously variable planetary device such as those described in reference to FIGS. 1-3, and disclosed in Patent Cooperation Treaty Application Number

PCT US 17/026,041, which is hereby incorporated by reference. As an illustrative example of a continuously variable drive, a schematic is depicted in FIG.5. It should be understood that there are a variety of architectures that the control and diagnostic methods described herein are applied to. In some embodiments, a continuously variable drive (CVD) 175 includes a continuously variable device 176 operably coupled to a multiple speed gear box or range box 177. In some embodiments, the continuously variable device 176 is controlled by the CVP control sub-module 110, and the multiple speed gear box 177 is controlled by the clutch control sub-module 108. It should be appreciated that the transmission control module 104 is optionally adapted to control both the continuously variable device 176 and the multiple speed gear box 117. The CVD 175 includes a first rotatable shaft 178 adapted to couple to a source of rotational power (not shown). The first rotatable shaft 178 forms a main axis. The continuously variable device 176 includes a variator 304 having a first traction ring assembly 305 and a second traction ring assembly 306. In some embodiments, the variator 304 is configured such as the variator depicted in FIGS. 1-3. The continuously variable device 176 includes a first planetary gear set 307 having a first ring gear 308, a first planet carrier 309, and a first sun gear 310. The first planetary gear set 307 is sometimes referred to herein as "the input split planetary gear set" having a ring to sun ratio represented by the term "RTS". The first ring gear 308 is operably coupled to the first traction ring assembly 305. The first planet carrier 309 is operably coupled to the first rotatable shaft 178. The first sun gear 310 is operably coupled to the second traction ring assembly 306. In some embodiments, the first sun gear 310 is operably coupled to a second rotatable shaft 179. The second rotatable shaft 179 is configured to couple to the multiple speed gear box 177. In some embodiments, the multiple speed gear box 177 is provided with a number of clutch devices including a forward mode clutch 180, a reverse mode clutch 181, a first-and-reverse mode clutch 182, a second- and-fourth mode clutch 183, and a third-and-fourth mode clutch 184. In some embodiments, the multiple speed gear box 177 includes a second planetary gear set 185. The second planetary gear set 185 has a second ring gear 186, a second planet carrier 187, and a second sun gear 188. In some embodiments, the second sun gear 188 is coupled to the third-and-fourth mode clutch 184 through a one-way clutch 194. The third-and-fourth mode clutch 184 is operably coupled to the forward mode clutch 180. The second ring gear 186 is coupled to the third-and-fourth mode clutch 184. In some embodiments, the multiple speed gear box 177 includes a third planetary gear set 189 having a third ring gear 190, a third planet carrier 191, and a third sun gear 192. The third sun gear 192 is coupled to the second-and-fourth mode clutch 183 and the reverse clutch 181. The third planet carrier 191 is coupled to the second ring gear 186. The third ring gear 190 is coupled to the second planet carrier 187. The third ring gear 190 and the second planet carrier 187 are adapted to couple to an output drive shaft 193. The output drive shaft 193 is adapted to transmit an output power from the CVD 175 through the range box 177.

Referring now to FIG. 6, during operation of the CVD 175 multiple modes of operation are achieved through engagement of the various clutching devices to provide modes corresponding to overlapping ranges of speed and torque. Typically, the first mode of operation corresponds to a launch mode of a vehicle from a stop. The subsequent modes engaged correspond to higher speed ranges. Likewise, the reverse mode of operation corresponds to a reverse direction of a vehicle equipped with the CVD 175. The table depicted in FIG. 6, lists the modes of operation for the CVD 175 and indicates with an "x" the corresponding clutch engagement or clutch position. For mode 1 operation, the forward mode clutch 180 and the first-and-reverse mode clutch 182 are engaged. For mode 2 operation, the forward mode clutch 180 and the second- and-fourth mode clutch 183 are engaged. For mode 3 operation, the forward mode clutch 180 and the third-and-fourth mode clutch 184 are engaged. For mode 4 operation, the forward mode clutch 180, the second-and-fourth mode clutch 183, and the third-and-fourth mode clutch 184 are engaged. For reverse mode operation, the first-and-reverse mode clutch 182 and the reverse mode clutch 181 are engaged.

Turning now to FIG. 7, in one embodiment, the transmission control module 104 includes a slip diagnostic process or method 200 configured to monitor and control a continuously variable drive, such as the one disclosed in reference to FIGS. 5 and 6. The slip diagnostic process 200 includes a block 201 where a number of input signals are received, for example, from the input signal processing module 102. In some embodiments, the input signals include, but are not limited to, an input shaft speed sensor (sometimes referred to herein as "Ni"), a CVP input or first traction ring speed sensor (sometimes referred to herein as "NCVP_R1"), and a transmission (CVD) output shaft speed sensor (sometimes referred to herein as "NTOSS"). In some embodiments, the input shaft speed sensor is located at the turbine shaft for converter equipped vehicles. In some embodiments, the input shaft speed is also the measured speed of the input split planetary carrier. In some embodiments, the first traction ring speed sensor is also the measured speed of the input split planetary ring gear. The slip diagnostic process 200 proceeds to a block 202 where the speed sensor signals are filtered.

Still referring to FIG. 7, the slip diagnostic process 200 proceeds to a block 203 where a calculation of the second traction ring speed is performed. The assumption is made that the input split planetary, such as the planetary gear set 307, is undamaged and the system is constrained such that if two planetary element speeds are known, the third is fully determined. For continuously variable drives such as those disclosed herein, a second traction ring, for example the second traction ring 306, is mechanically coupled to the sun gear 310 of the input split planetary gear set 307. This enables the elimination of a ring speed sensor from the CVP downstream of the input planetary. Recognizing that the input planetary carrier 309 speed is the weighted average of the ring gear 308 and sun gear 310 speeds yields the following relationship.

Nj(Rl + SI) = N _{CVP R1} (R1) + N _S1 (S1)

Rearranging to solve for the sun gear speed (Nsi) and second traction ring speed

Nsi = cvp _R2 = Ni(l + RTS) - N _{CVP R1} (RTS)

Still referring to FIG. 7, in some embodiments, the slip diagnostic process 200 proceeds in parallel to a block 204, a block 205, a block 206, and a block 207. In the block 204, a speed ratio of the CVP, for example the CVP 304, is calculated by dividing the second traction ring speed (NCVP_R2) by the first traction ring speed (NCVP_RI)- I ⁿ the block 205, a speed ratio of the continuously variable drive, for example CVD 175, is calculated by dividing the second traction ring speed (NCVP_R2) by the input shaft speed (Ni). In the block 206, the speed (backward path) of the sun gear, for example the sun gear 310, is calculated by multiplying the transmission output speed (NTOSS) by a current speed ratio (SR _ra nge_box) of the multiple speed gear box, for example the gear box 177.

In the block 207, a slip speed of a CVD lock-up clutch, for example a clutch operably coupled to the CVP 304 and the planetary gear set 307 to enable lock-up operation, is calculated. For illustrative examples of a CVP lock-up clutch, see Patent Cooperation Treaty Application No. PCT US 17/031,666, which is hereby incorporated by reference. In some embodiments, as shown in FIG. 8, the lock-up clutch 311 is coupled to the planet gear set 307 through the planet carrier 83 and the sun gear 84. In some embodiments, the lock-up clutch is operably coupled to the ring gear and the planet carrier of the planetary gear set. Additional configurations of the coupling of the lock-up clutch and the planetary gear set are described in Patent Cooperation Treaty Application No. PCT/US 17/031 ,666. It should be appreciated that the lock-up clutch disclosed herein are optionally configured as wet clutch, dry clutches, synchronizer clutches, one-way clutches, or mechanical diodes.

In some embodiments, the block 207 calculates the CVD lock-up clutch slip speed (N _s ii _P _cvD) by subtracting the first traction ring speed from the input shaft speed (NO-

Referring back to FIG. 7, in some embodiments, the slip diagnostic process 200 proceeds from the block 204 to a block 208 where a CVP speed ratio error is determined by comparing a commanded CVP speed ratio (SRcvp_command) to a measured CVP speed ratio (SRcvp actuai). The block 205 proceeds to a block 209 where a CVD speed ratio error is determined by comparing a commanded CVD speed ratio

(SRcvD_command) to a measured CVD speed ratio (SRcvD_actuai). The block 206 proceeds to a block 210 where a sun gear speed (forward path) is calculated by multiplying the input shaft speed (Ni) by the CVD ratio (CVD _ra tio). The slip diagnostic process 200 proceeds from the block 210 to a block 217 where the sun speed determined in the block 206 is compared to the sun speed determined in the block 210. It is noted that the sun gear speed is calculated in two process blocks, sometimes referred to herein as a forward path through the block 210 and a backward path through the block 206.

Theoretically the sun gear speed calculated form the forward path through the input speed (block 210) should be equal to the sun gear speed calculated through the backwards path through the TOSS sensor (block 206). A disagreement between these two calculations indicates that one or more elements in the multiple speed range box is slipping. Therefore, if the two speeds are not equal, the block 217 passes a multiple speed gear box slip fault 218 to the transmission control module 104. The block 207 proceeds to a block 21 1 where a slip is the CVD lock-up clutch is evaluated. If the CVD lock-up clutch slip speed (Nsiip cvo) is greater than zero, or a calibrateable threshold variable (not shown), then the block 21 1 returns a CVD lock-up clutch slip fault 219 to the transmission control module 104. It should be appreciated that the comparison of errors, such as performed in the block 208, the block 209, the block 217, and the block 21 1 , are optionally configured to include a comparison to pre-determined calibrateable threshold variables.

Still referring to FIG. 7, in some embodiments, the slip diagnostic process 200 includes a block 212 adapted to receive signals from the block 208 and the block 209. The block 212 evaluates the CVP speed ratio error and the CVD speed ratio error to determine a number of fault conditions. For example, if there is no CVP speed ratio error and CVD speed ratio error passed from the blocks 208 and 209, respectively, then the block 212 passes a no fault signal 213 to the transmission control module 104. If there is no CVP speed ratio error, but there is a CVD speed error, then the block 212 passes a CVD input planetary damage fault 214 to the transmission control module 104. Because the CVD ratio and CVP ratio are mechanically coupled, if there is no CVP slip, if the CVP ratio is correct while the CVD ratio is in error, the process indicates that the planetary itself is damaged. If there is a CVP speed ratio error and no CVD speed ratio error, then the block 212 passes a CVP small slip fault 215 to the

transmission control module 104. This condition indicates that the CVP slip is of sufficiently small magnitude that the CVD closed loop control structure is capable of compensating by altering the CVP speed ratio reference. If the there is a CVP speed ratio error and a CVD speed ratio error, the block 212 returns a CVP gross slip fault 216 to the transmission control module 104. This condition indicates that the CVP slip is of sufficiently large magnitude that the CVD closed loop control structure is incapable of compensating by altering the CVP speed ratio reference.

Passing now to FIG. 9, and still referring to FIG. 7, a table is shown that depicts the fault conditions discussed previously. In a no fault condition 213", the transmission control module 104 operates in a normal mode of operation as programmed. When the transmission control module 104 receives a fault command such as those listed in the table and described herein, there are a number of mitigation actions that the

transmission control module 104 is capable of managing. For example, during a CVD lock-up clutch slip fault 219, the transmission control module 104 optionally issues commands to disallow engagement of the lock-up clutch. In some embodiments, case 2 prohibits the operation of a fixed gear launch or a towing mode of operation. During the multiple speed gear box clutch slip fault 218, the transmission controller 104 optionally issues commands to reduce torque delivered to the multiple speed gear box by lowering input torque or adjust the ratio of the CVP. The transmission controller 104 optionally issues commands to adjust hydraulic control pressure to maximum line pressure. The transmission controller 104 optionally disallows certain operating modes of the multiple speed gear box, or shorten shift times between operating modes. During the CVP gross slip fault 216 or the CVP small slip fault 215 the transmission controller 104 optionally issues commands to reduce input torque, increase hydraulic pressure for clamping, adjust speed ratio of the CVP, and/or engage the lock-up clutch. During the input planetary damage fault 214, the transmission controller 104 issues commands to command a neutral position for the multiple speed gear box, for example.

The foregoing description details certain embodiments. It will be appreciated, however, that no matter how detailed the foregoing appears in text, the preferred embodiments are practiced in many ways. As is also stated above, it should be noted that the use of particular terminology when describing certain features or aspects of the preferred embodiments should not be taken to imply that the terminology is being redefined herein to be restricted to including any specific characteristics of the features or aspects of the preferred embodiments with which that terminology is associated.

While preferred embodiments have been shown and described herein, it is obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the preferred embodiments. It should be understood that various alternatives to the preferred embodiments described herein can be employed in practicing the preferred embodiments. It is intended that the following claims define the scope of the preferred embodiments and that methods and structures within the scope of these claims and their equivalents be covered thereby.