CONTROL OF A POWER TAILGATE SYSTEM RESPONSIVE TO CLUTCH SLIPPAGE

A system for controlling a power tailgate in a vehicle power tailgate system includes a motor, a reduction drive, and a slippable clutch. A screw is connected to the clutch. The clutch is structured to transmit torque between the reduction drive and the screw. A slide is connectible to a tailgate and connected to the screw so that rotation of the screw produces a linear extension or retraction of the slide. The system includes a tailgate control module including instructions to, responsive to an input from a user, control operation of the motor to attempt to lower or raise the tailgate, determine whether the clutch slipped by at least a predetermined slip amount during operation of the motor and, responsive to a determination that the clutch slipped by at least the predetermined slip amount, generate an alert indicating a need for manual reset of the tailgate.

TECHNICAL FIELD

The embodiments disclosed herein relate to vehicles with tailgates and, more particularly, to tailgate control systems for automatically opening the tailgates and automatically closing the tailgates.

BACKGROUND

Many vehicles include tailgates. The tailgate is rotatably connected to the vehicle and is movable between closed positions and open positions to serve as a closure panel for a rear portion of the vehicle. Many of today’s vehicles have power tailgates included as part of power tailgate systems. The power tailgate system includes motor-driven tailgate actuators for the tailgates, and motor-driven latch actuators for the latch assemblies. By the operation of the tailgate actuators and the latch actuators, the power tailgate system automatically opens the tailgate and automatically closes the tailgate. Tailgate opening commands to the power tailgate system may be initiated by a user using a switch inside the vehicle or a keyfob.

Operation of the motor (expressed, for example, as a number of rotations of a motor armature) may be associated with motions of the tailgate, so that it is known how many armature rotations correspond to each predefined motion of the tailgate (for example, movement of the tailgate between fully closed and fully open positions). During operation of the power tailgate system, application of external forces (i.e. forces other than those exerted by the actuator motor) to the tailgate may cause backdriving of the motor. If this backdriving is severe enough, it may damage the motor. A slippable clutch may be interposed at some point between the motor and the tailgate to enable motion of the tailgate independent of the motor when the applied external forces are large enough to otherwise damage the tailgate. However, if the applied forces are large enough to cause the clutch to slip, the synchronization and association between the motor rotation and the tailgate motion may be disrupted to the point where a desired positon of the tailgate is no longer provided by operating the motor for the associated number of armature rotations.

SUMMARY

In one aspect of the embodiments described herein, a system for controlling a power tailgate in a vehicle power tailgate system is provided. The system includes a motor, a reduction drive operably connected to the motor, and a slippable clutch operably connected to the reduction drive. A screw is operably connected to the clutch. The clutch is structured to transmit torque between the reduction drive and the screw. A slide is operably connectible to a tailgate and operably connected to the screw so that rotation of the screw produces an associated linear extension or retraction of the slide. The system also includes a processor and a memory communicably coupled to the processor. The memory stores a tailgate control module including instructions that when executed by the processor cause the processor to, responsive to an input from a user, control operation of the motor to attempt to lower or raise the tailgate, determine whether the clutch slipped by at least a predetermined slip amount during operation of the motor to attempt to lower or raise the tailgate and, responsive to a determination that the clutch slipped by at least the predetermined slip amount, generate an alert indicating a need for manual reset of the tailgate.

DETAILED DESCRIPTION

A system for controlling a power tailgate in a vehicle power tailgate system includes a motor, a reduction drive operably connected to the motor, and a slippable clutch operably connected to the reduction drive. A screw is operably connected to the clutch. The clutch is structured to transmit torque between the reduction drive and the screw. A slide is operably connectible to a tailgate and operably connected to the screw so that rotation of the screw produces an associated linear extension or retraction of the slide. The system also includes a processor and a memory communicably coupled to the processor. The memory stores a tailgate control module including instructions that when executed by the processor cause the processor to, responsive to an input from a user, control operation of the motor to attempt to lower or raise the tailgate, determine whether the clutch slipped by at least a predetermined slip amount during operation of the motor to attempt to lower or raise the tailgate and, responsive to a determination that the clutch slipped by at least the predetermined slip amount, generate an alert indicating a need for manual reset of the tailgate. An excessive slippage of the clutch during tailgate movement may be detected based on parameters such as a known number of motor armature rotations expected for a desired movement of the tailgate from a first predefined position to a second predefined position, a number of armature rotations actually detected during the desired movement, and a current position of the tailgate. Also disclosed is a method for controlling a vehicle power tailgate, the method including steps of controlling operation of a motor to attempt to lower or raise the tailgate operably connected to the motor, determining that a clutch interposed between the motor and the tailgate (and operably connected to the motor and the tailgate) slipped by at least a predetermined slip amount during operation of the motor to attempt to lower or raise the tailgate, and responsive to the determination that the clutch slipped by at least the predetermined slip amount, generating an alert indicating a need for manual reset of the tailgate.

Referring toFIG.1A, an example of a vehicle100is illustrated. In one or more implementations, the vehicle100is pickup truck with a rear tailgate that may be automatically lowered (i.e., “opened”) and raised (i.e., “closed”). The terms “open”, “opened”, “opening”, etc. and “lower”, “lowered”, “lowering”, etc. may be used interchangeably herein as applied to the tailgate. Similarly, the terms “close”, “closed”, “closing”, etc. and “raise”, “raised”, “raising”, etc. may be used interchangeably herein as applied to the tailgate. The vehicle100can have any combination of the various elements shown inFIG.1A. Further, the vehicle100can have additional elements to those shown inFIG.1A. In some arrangements, the vehicle100may be implemented without one or more of the elements shown inFIG.1A. While the various elements are shown as being located within the vehicle100inFIG.1A, it will be understood that one or more of these elements can be located external to the vehicle100.

Additionally, it will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals may have been repeated among the different figures to indicate corresponding or analogous elements. In addition, the discussion outlines numerous specific details to provide a thorough understanding of the embodiments described herein. Those of skill in the art, however, will understand that the embodiments described herein may be practiced using various combinations of these elements.

Part of the exemplary passenger vehicle100is shown inFIG.1B. As shown, the vehicle100is a pickup truck. The vehicle100includes an exterior and several interior compartments. In the illustrated pickup truck configuration of the vehicle100, the compartments include an open-topped bed102for carrying cargo. In addition to the bed102, the compartments may include a passenger compartment, an engine compartment and the like. Among other things, the vehicle100may include seats, a dash assembly, an instrument panel and the like housed in the passenger compartment. In addition, the vehicle100may include an engine, a transmission and the like, as well as other powertrain components (such as wheels, for example) housed in the engine compartment and elsewhere in the vehicle100. The wheels support the remainder of the vehicle100on the ground. One or more of the wheels may be powered by the remainder of the powertrain components to drive the vehicle100along the ground.

The vehicle100may include a body104that forms the exterior and defines or otherwise encloses the bed102and the other compartments. In relation to the bed102, the body104includes a deck or cargo bed106, two sidewalls108, a bulkhead110and a rear end112. At the rear end112, the body104defines a tailgate opening114. Likewise, the body104, including but limited to the sidewalls108, renders surrounding body116that frames the tailgate opening114. The tailgate opening114opens between the bed102and the exterior. Relatedly, as part of the rear end112, the body104includes a tailgate118corresponding to the tailgate opening114.

As shown with reference toFIGS.1B and1C, the tailgate (or “TG”)118serves as closure panel for the bed102. The tailgate118is pivotally connected to the surrounding body116for movement, relative to the tailgate opening114, between a fully closed, raised, or “up” position and a fully open, lowered, or “down”) position through a range of partially-open positions. InFIG.1C, the tailgate118is shown in the fully closed or raised position. In the fully closed position, the tailgate118is positioned over the tailgate opening114, with the periphery of the tailgate118adjacent to the surrounding body116, and the tailgate118in alignment with the surrounding body116. Also, in the fully closed position, the tailgate118may be in a position in which it can be secured by one or more latches to maintain the tailgate in a vertical or near-vertical orientation adjacent the sidewalls108of the cargo bed, thereby closing off an end of the cargo bed. InFIG.1B, the tailgate118is shown in the fully open or lowered position. In the fully open position, the tailgate118is positioned away from the tailgate opening114, which allows access to the bed102from the rear of the vehicle100. In the fully open position, the tailgate may be supported by cables or other supports to reside in a horizontal or near-horizontal orientation, which facilitates loading and/or removal of cargo. InFIG.1D, the tailgate118is shown in a representative partially-open position. In the partially-open positions, the tailgate118is between the fully closed position and the fully open position.

As shown, with reference toFIGS.1B and1C, in relation to opening the tailgate118and closing the tailgate118, the vehicle100includes a hinge assembly120, and an in-bed tailgate actuator122. Serving, at least in part, as a basic hinge, the hinge assembly120runs between the bed102and the tailgate118. The hinge assembly120connects the tailgate118to the bed102, and thereby supports the tailgate118from the bed102for rotational movement between the closed position and the open position. The tailgate actuator122corresponds to the hinge assembly120and may be housed, in whole or in part, in the bed102. From inside the bed102, the tailgate actuator122is connected to the tailgate118through the hinge assembly120. Although the vehicle100, as shown, includes one hinge assembly120, and one tailgate actuator122, it will be understood that this disclosure is applicable in principle to otherwise similar vehicles including one or more hinge assemblies120, and one or more tailgate actuators122.

Referring toFIG.1C, in one or more arrangements, the hinge assembly120may include a rotatable element301structured for transmitting rotational force to the tailgate. In one or more arrangements, the rotatable element may be rotary through-bed torque shaft incorporated into the hinge assembly120for operable connection with the tailgate. In other arrangements, the rotatable element may be another rotatable portion of the hinge assembly structured for operable connection with the tailgate, depending on the particular hinge assembly design. The rotatable element301may be axially aligned with the pivotal movement of the tailgate118, and supported from the bed102for axial rotation. The rotatable element301may support the tailgate118for rotation about an associated rotatable element rotational axis399, as shown inFIG.1C. Moreover, the hinge assembly120may also include a pivotal in-bed crank307operably connected to the rotatable element301along the rotational axis399of the rotatable element301so that a rotation of the crank307produces a corresponding rotation of the rotatable element301about the axis399(i.e., rotating the crank30715° about the rotatable element rotational axis399produces a corresponding rotation of the rotatable element30115° about the axis). From outside the bed102, the rotatable element301may be connected to and support the tailgate118from the bed102. From inside the bed102, the tailgate actuator122is connected between the bed102and the crank307. Moreover, the bed102, the tailgate actuator122and the crank307serially share pivotal connections. The rotatable element301may transmit torque and rotation associated with the pivotal movement of the tailgate118between the tailgate and the crank307. The term “operably connected,” as used throughout this description, can include direct or indirect connections, including connections without direct physical contact. Similarly, elements described as being “operably connectible” are elements that can be connected directly (through direct physical contact) or indirectly, through other, physically intermediate element(s).

With the bed102, the tailgate actuator122and the crank307serially sharing pivotal connections, from between the bed102and the crank307, as the product of extending and retracting as described herein, the tailgate actuator122is operable to pivot the crank307against the bed102. With the tailgate118, the rotatable element301and the crank307serially sharing rotary connections, as the crank307pivots, the rotatable element301axially rotates, and, as the rotatable element301axially rotates, the tailgate118pivotally closes, pivotally opens, and otherwise pivotally moves between the open position and the closed position.

In one or more arrangements, the hinge assembly may be structured as described in pending commonly-owned U.S. Pat. Application No. 16/883,246, the disclosure of which is incorporated by reference herein in its entirety.

The vehicle100may include a tailgate actuator122. The tailgate actuator122may be connected to the vehicle energy system150as described herein. Moreover, the tailgate actuator122may be connected to the tailgate118through the hinge assembly120and its rotatable element301. Through the hinge assembly120, the tailgate actuator122may be operable to open the tailgate118, close the tailgate118and otherwise move the tailgate118between the closed position and the open position using electrical energy from the energy system150. Although the vehicle100, as shown, includes one tailgate actuator122, it will be understood that this disclosure is applicable in principle to otherwise similar vehicles including one or more tailgate actuators122.

With reference toFIG.2, in one implementation, the tailgate actuator122may be a linear actuator. In particular arrangements, the linear actuator may be in the form of a motor-driven spindle drive operable to extend and retract in a reciprocating motion.

The tailgate actuator122may include a two-piece telescoping or otherwise extensible housing200. The housing200may include a tubular base202, a tubular slide204, and a sliding overlap206therebetween. Inside the housing200, the tailgate actuator122may include axially aligned items for converting rotary movement into linear extension and retraction. The tailgate actuator122may include a motor210, a reduction drive212, a clutch298, a rotary screw214, and a fixed nut216. The motor210and the reduction drive212may be secured with the base202, the nut216may be secured with the slide204, and the screw214may run through the nut216. The base202and the nut216may support the screw214for axial rotation, including powered axial rotation by the motor210through the reduction drive212and the clutch298. In one implementation, the reduction drive212may be a planetary reduction drive. For instance, the reduction drive212may be a multistage planetary reduction drive. In one implementation, the screw214may be a ball screw, and the nut216may be a ball nut.

In one or more particular arrangements, the reduction drive212may be configured so that eighteen motor armature rotations produce one rotation of the portion of the reduction drive operably connected to the clutch (and, therefore, one rotation of the screw214) (i.e., a conversion ratio of 18:1). Alternatively, conversion ratios other than 18:1 may be used. In addition, the screw214, slide204, and nut216may be structured such that a single rotation of screw214by the reduction drive212produces an associated 9 millimeter linear travel of the slide204, in both the extension direction and the retraction direction.

A motor circuit203may be provided for implementing motor switching and other electrical operations of the motor responsive to control commands received from the tailgate control module323, as shown inFIG.1A.

As used herein, the term “backdrive” may refer to application of an external force producing a linear movement of the slide204which generates a torque in the screw, resulting in an associated rotation of the reduction drive212operably connected to the screw and a resulting rotation of an armature (not shown) of the motor210operably connected to the reduction drive212. If the backdrive rotation rate of the armature is above a first predetermined threshold TH1, the motor210may be damaged. The external backdriving force may be applied to the slide204by applying an external force to the tailgate operably coupled to the slide204. For example, a user may manually apply an opening or closing force to the tailgate118, or a load in the cargo bed may bear on the tailgate118to apply a force in the opening direction.

In embodiments described herein, to aid in preventing damage to the motor210due to backdrive, a clutch298may be interposed between (and operably connected to) the reduction drive212and the screw214. A first portion298aof the clutch298may be rigidly attached to a portion of the reduction drive212that would otherwise be directly operably connected to the screw214to transmit torque to the screw (and to receive torque from the screw). A second portion298bof the clutch298may be rigidly attached to the portion of the screw214that would otherwise be directly operably connected to the reduction drive212to transmit torque to the reduction drive (and to receive torque from the reduction drive).

The clutch298may be structured to transmit torque in either rotational direction from the reduction drive212to the screw214during normal operations to open and close the tailgate118. The clutch298may also be structured to transmit torque from the screw214to the reduction drive212when the screw214is back-driven by application of an axial load to the slide204sufficient to cause a rotation of the motor armature that is below the first predetermined threshold TH1 rotation rate. Also, for situations where the magnitude and/or rate of application of the axial load applied through the slide204is sufficient to generate a backdrive torque that rotates the armature at a rate above the first predetermined threshold TH1, the clutch298may be structured to “slip” to enable rotational motion of the combination of the screw214and the second portion of the clutch298battached to the screw, independent of (and with respect to) the combination of the first portion298aof the clutch298and the portion of the reduction drive212attached to the first portion of the clutch. This configuration may act to prevent damage to the motor210due to backdriving of the actuator in situations where the applied torque would otherwise cause an armature rotation rate exceeding the first predetermined threshold TH1.

Slippage of the clutch298enables the first portion298aof the clutch298and the portion of the reduction drive212attached thereto to rotate independently of the second portion298bof the clutch298and the portion of the screw214attached thereto, for as long as the applied torque equals or exceeds the torque level associated with the first predetermined threshold armature rotation rate TH1. In embodiments described herein, the clutch298may be structured to slip in either of opposite rotational directions. That is, the second portion298bof the clutch298may be structured to slip in the same direction of rotation as the first portion298aof the clutch298, and may be configured to slip in a direction opposite the direction of rotation of the first portion298aof the clutch298. The direction of rotation of the first portion of the clutch will depend on the direction in which the motor210is turning, to either raise or lower the tailgate. During normal (i.e., non-slip) operation of the tailgate control system to raise and lower the tailgate, the second portion298bof the clutch298will rotate in the same direction as the first portion298aof the clutch298. The direction in which the second portion298bof the clutch slips will depend on the direction of the external force applied to the tailgate, as described herein.

The “slip torque” of the clutch298may be a torque at or above which the second portion298bof the clutch will rotationally slip or slide with respect to the first portion298aof the clutch, thereby enabling independent rotation of the combination of the screw214and the second portion298bof the clutch298attached to the screw214with respect to the combination of the first portion298aof the clutch298and the portion of the reduction drive212attached to the first portion of the clutch. In some embodiments of the clutch298, the clutch may be adjustable to enable the slip torque to be tailored to the requirements of a specific application or tailgate control system. The slip torque associated with a specified threshold armature rotation rate TH1 may be determined analytically and/or experimentally and the clutch may be adjusted or modified to slip at or close to the desired torque. The desired torque may be defined as a specific value, a value with a tolerance range, or a larger torque value range beyond ordinary mechanical tolerances. Determination of the first predetermined threshold TH1 needed to prevent motor damage for a given application may be determined by analysis and/or experimentation using known methods, and with reference to the characteristics of the reduction drive212and the motor210.

In one or more arrangements, the clutch298may be a friction-based slip clutch structured to “slip” and enable relative rotational motion of the screw with respect to a portion of the reduction drive. Alternatively, any type of clutch suitable for the purposes described herein may be used. One source of clutches suitable for the applications described herein is Dynatect Manufacturing, Inc. of New Berlin, WI.

The motor210may be operable to drive the tailgate actuator122to extend and retract. The motor210may be operable to spin, and thereby power the axial rotation of the screw214through the reduction drive212. As the screw214axially rotates, the nut216axially moves along the screw214and, as the nut216axially moves along the screw214, the base202and the slide204are alternately drawn apart and drawn together. As the base202and the slide204are drawn apart, the tailgate actuator122is extended. Alternately, as the base202and the slide204are drawn together, the tailgate actuator122is retracted.

From inside the bed102, the tailgate actuator122is configured to reach between the bed102and the crank307. As the product of extending and retracting, the tailgate actuator122is operable to pivot the crank307against the bed102. Likewise, to allow the tailgate actuator122to extend and retract in association with pivoting the crank307against the bed102, the bed102, the tailgate actuator122and the crank307serially share pivotal connections. Accordingly, the bed102and the tailgate actuator122are configured to make a pivotal connection with one another. Specifically, with reference toFIG.2, the bed102may include a bracket-mounted ball stud350, the tailgate actuator122includes a ball socket352, and the ball stud350and the ball socket352are configured to make a ball-and-socket connection with one another. Moreover, the crank307and the tailgate actuator122are configured to make a pivotal connection with one another. Again, with reference toFIG.2, the crank307includes the ball stud348, the tailgate actuator122includes a ball socket354, and the ball stud348and the ball socket354are configured to make a ball-and-socket connection with one another.

As set forth herein, as the product of extending and retracting, the tailgate actuator122is operable to pivotally close the tailgate118, pivotally open the tailgate118, and otherwise pivotally move the tailgate118between the open position and the closed position. As the tailgate118is pivotally closed, the associated pivotal movement of the tailgate118is against gravity. Likewise, as the tailgate118is pivotally opened, the associated pivotal movement of the tailgate118is with gravity.

Moreover, as shown with reference toFIG.1D, the vehicle100may include one or more tailgate-side latch assemblies130. Each latch assembly130may include a striker chute132and a corresponding latch134for latching the tailgate118. Relatedly, the vehicle100may include one or more vehicle-side strikers136corresponding to the striker chutes132and the latches134. Each latch assembly130is connected to the tailgate118. Each latch assembly130may be housed, in whole or in part, in the tailgate118. For instance, each latch assembly130may be housed in the tailgate118, and connected to the tailgate118, as a unitary module. Each striker136is connected to the surrounding body116. Although the vehicle100, as shown, includes two latch assemblies130and two strikers136, it will be understood that this disclosure is applicable in principle to otherwise similar vehicles including one or more latch assemblies130and one or more strikers136.

For each corresponding striker chute132, latch134and striker136, the striker chute132opens to the tailgate118for passing the striker136into and out of the tailgate118. The latch134is movable, relative to the striker chute132, in a latching direction and in an unlatching direction between an unlatching position and a latching position. InFIG.1D, the latch134is shown in the unlatching position. In the unlatching position, the latch134aligns with the striker chute132for passing the striker136into and out of the tailgate118. In the latching position, the latch134crosses the striker chute132for capturing the striker136within the tailgate118. Accordingly, the latch134latches the tailgate118to the surrounding body116against the striker136.

The latch134may be activated for non-revertible movement in the latching direction. When the tailgate118is being closed, the latch134functions as the tailgate118is moved to the closed position, and afterward, when the tailgate118is in the closed position. With the tailgate118in the open position, the latch134, having previously unlatched the tailgate118, is in the unlatching position. To close the tailgate118, the latch134is activated for non-revertible movement in the latching direction. As the tailgate118is moved to the closed position, the striker136passes into the tailgate118through the striker chute132. As it passes into the tailgate118, the striker136moves the latch134in the latching direction to the latching position, and the latch134, unable to move in the unlatching direction to the unlatching position, latches the tailgate118to the surrounding body116against the striker136.

In addition, the latch134may be deactivated for movement in the unlatching direction. When the tailgate118is being opened, the latch134functions as the tailgate118is moved to the open position. With the tailgate118in the closed position, the latch134, having previously latched the tailgate118, is in the latching position. To open the tailgate118, the latch134is deactivated for movement in the unlatching direction. As the tailgate118is moved to the open position, the striker136passes out of the tailgate118through the striker chute132. As it passes out of the tailgate118, the striker136, in combination with a bias for movement in the unlatching direction, moves the latch134in the unlatching direction to the unlatching position, and the latch134unlatches the tailgate118from the surrounding body116from against the striker136.

The vehicle100may include one or more latch actuators154for the latch assemblies130. Each latch actuator154corresponds to a latch assembly130, and may be housed, in whole or in part, in the tailgate118. For instance, each latch actuator154may be housed in the tailgate118, and connected to the tailgate118, as a unitary module with the corresponding latch assembly130. In one implementation, each latch actuator154is a motor-driven reduction drive. In this and other implementations, each latch actuator154is connected to the energy system. Moreover, each latch actuator154may be connected to the corresponding latch assembly130. For each corresponding latch assembly130, latch134and latch actuator154, using electrical energy from the energy system150, the latch actuator154is operable to activate the latch134for non-revertible movement in the latching direction, and deactivate the latch134for movement in the unlatching direction. Although the vehicle100, as shown, includes one latch actuator154per latch assembly130, it will be understood that this disclosure is applicable in principle to otherwise similar vehicles including one or more latch actuators154per latch assembly130.

One or more arrangements of the power tailgate system may be structured to enable a command to automatically raise the taligate118from the fully-open position to a half-latched position, which is a near-closed (but not fully closed) position of the tailgate. Latch assemblies130of the vehicle100may also be structured to maintain the tailgate in the half-latched /near-closed position. Examples of latch assemblies suitable for securing the tailgate in a half-latched position and controllable for the purposes described herein may be found in commonly-owned U.S. Pat. Application Nos. 17/335549, 17/335529, and 17/335545, the disclosures of which are incorporated herein by reference in their entireties. Other types of latch structures are also contemplated. Exemplary control operations of the tailgate118responsive to application of an external force when raising the tailgate to the half-latched position are also described herein.

The vehicle100can include one or more processors144. In one or more arrangements, the processor(s)144can be a main processor(s) of the vehicle100. For instance, the processor(s)144can be an electronic control unit (ECU). The vehicle100can include one or more data stores327for storing one or more types of data. The data store(s)327can include volatile and/or non-volatile memory. Examples of suitable data store(s)327include RAM (Random Access Memory), flash memory, ROM (Read Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable Programmable Read-Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), registers, magnetic disks, optical disks, hard drives, or any other suitable storage medium, or any combination thereof. The data store(s)327can be a component of the processor(s)144, or the data store(s)327can be operably connected to the processor(s)144for use thereby.

The one or more data store(s)327can include sensor data331, as shown inFIG.1A. In this context, “sensor data” means any information about the sensors that the vehicle100is equipped with, including the capabilities and other information about such sensors. As will be explained below, the vehicle100can include the sensor system142. The sensor data331can relate to one or more sensors of the sensor system142. As an example, in one or more arrangements, the sensor data331can include information on the tailgate position sensor379of the sensor system142. The one or more data store(s)327can also include lookup tables329, as indicated inFIG.1A, equations, and other information stored to be accessible by sensors of the sensor system142and/or the tailgate control module323in performing the operations described herein.

In addition, during design, assembly, and/or configuration of the actuator122, the number of motor rotation edges that will be generated during raising and lowering of the tailgate118to various predetermined positions may be determined and stored for purposes described herein. These values may be determined using known methods through testing of the actuator122, and a nominal or average value assigned to a variable representing the number of motor rotation edges expected to be detected during each given movement of the tailgate. For example, a number of motor rotation edges expected to occur during lowering of the tailgate118from the fully closed position to the fully open position may be determined and assigned to the variable “EEO”. A number of motor rotation edges expected to occur during raising of the tailgate118from the fully open position to the fully closed position may be determined and assigned to the variable “EEC”. A number of motor rotation edges expected to occur during raising of the tailgate from the fully open position to a half-latched position may be determined and assigned to the variable “EEH”.

In addition, an associated tolerance value may be assigned to each expected number of motor rotation edges to account for slight variations in the number of edges detected during movement of the tailgate118between the various predetermined positions during testing. A suitable tolerance value may for each actuator configuration and type of tailgate movement may be determined based on analysis, testing, and/or experimentation. Associated tolerance values TEEO, TEEC, and TEEH may be assigned to the respective variables EEO, EEC, and EEH. Each tolerance value may be defined to encompass the entire range of motor rotation edge values after which the tailgate can be considered to have moved from one position (e.g., fully closed) to another position (e.g., fully open). For example, in one application, it may be determined by experimentation that a tailgate will have been moved from the fully closed position to the fully open position after 100 ± 5 motor rotation edges have been detected. The various values of expected motor rotation edges and associated tolerances may be stored in data stores327, for example, in lookup tables329, for comparison with actual numbers of motor rotation edges detected during attempts by the tailgate control system to move the tailgate responsive to user commands, as described herein.

In embodiments described herein, the memory146may be a random-access memory (RAM), read-only memory (ROM), a hard-disk drive, a flash memory, or other suitable memory for storing modules, such as the tailgate control module323. The tailgate control module323includes, for example, computer-readable instructions that when executed by the processor144, cause the processor(s)144to perform the various functions disclosed herein. Additional modules (not shown) may also be stored in memory146. For example, as part of a central control system, the vehicle100may include a global control unit (GCU) to with which the tailgate control module323is communicatively connected.

The vehicle100can include one or more modules, at least some of which are described herein. The module(s) may be stored in memory146. The modules can be implemented as computer-readable program code that, when executed by processor(s)144, implement one or more of the various processes described herein. One or more of the modules can be a component of the processor(s)144, or one or more of the modules can be executed on and/or distributed among other processing systems to which the processor(s)144is operably connected. The modules can include instructions (e.g., program logic) executable by one or more processor(s)144. Alternatively, or in addition, one or more of data store(s)327or another portion of the vehicle100may contain such instructions.

The vehicle100can include the tailgate control module (TCM)323. The tailgate control module323may be configured to receive tailgate opening and closing commands, and to automatically control opening and closing operations of the tailgate118. The processors144, the memory146and the tailgate control module323as described herein together may serve as a computing device whose control module323is employable to orchestrate the operation of the tailgate118. Specifically, the tailgate control module323may control operation of the vehicle systems140based on information about the vehicle100(including the position and/or speed of the tailgate), received tailgate control signals, and other information. Accordingly, as a prerequisite to operating the tailgate, the control module323gathers and/or receives information, including the information about the vehicle100detected by the sensor system142. The control module323may also be configured to receive commands from a human user and/or from other modules or elements of the vehicle. The commands may be remotely generated (i.e., generated by a user, system, element, or other entity external to the vehicle). The control module323may then evaluate the information and operate the various vehicle systems and elements (including the tailgate118) based on its evaluation, with a view to controlling operations of the tailgate.

The tailgate control module323may include instructions that when executed by the processor(s)144cause the processor(s)144to, responsive to an input from a user, control operation of the motor210to attempt to lower or raise the tailgate118. The input from the user may be the pushing of a suitable button mounted in the vehicle or on a key fob, for example. The user input may generate a command instructing the tailgate control module323to control the motor210. The tailgate control module323may also include instructions to determine whether the clutch298slipped by at least a predetermined slip amount during operation of the motor210to attempt to lower or raise the tailgate118. The tailgate control module323may also include instructions to, responsive to a determination that the clutch slipped by at least the predetermined slip amount during operation of the motor210to attempt to lower or raise the tailgate118, generate an alert indicating a need for manual reset of the tailgate.

Alerts and generated signals indicating the need for a manual reset of the tailgate118may be in any of a variety of forms, including audible alerts, visual alerts, or a combination thereof. The alert(s) may be conveyed via a display screen, an audible alarm mounted on the vehicle, through a cellular device of the user, or by any other suitable means.

The “predetermined slip amount” may be an amount of slip which will cause the difference between an expected number of motor rotation edges to perform a command and an actual number of motor rotation edges detected when attempting to perform the command, to equal or exceed the tolerance value attached to the expected number of motor rotation edges. Ideally, the actual number of motor rotation edges detected when attempting to perform the movement command should be within the tolerance range of the number of motor rotation edges expected to be detected when performing the movement command. This condition should be satisfied when there is little or no clutch slip during tailgate movement, because the tolerance range may encompass all values of the expected number of motor rotation edges that will bring the tailgate into a desired position.

Any amount of clutch slippage will disrupt the rotational synchronization of the screw214with the reduction drive212, resulting in a difference between the number of motor rotation edges actually detected in moving the tailgate to a desired position, and the number of motor rotation edges expected to be detected when moving the tailgate to the desired position. In cases where clutch slippage is very minor, difference in the number of motor edge rotations may be within the tolerance of the expected number of rotations. However, in cases where the clutch slips excessively due to application of an external force, the tailgate118may either fail to reach a desired position, or the tailgate may reach the desired position sooner than would be indicated by the expected number of motor rotation edges required to make the required movement. In such cases, a manual reset of the tailgate system may be necessary in order for the tailgate to function automatically in response to user commands. These principles are illustrated inFIGS.4A-7B.

FIG.4Ais a schematic side view of a rear portion of the vehicle100showing fully closed (118c), fully open (118z), and intermediate positions of a tailgate118. InFIG.4A, the tailgate118is acted on by an opening force MF1 generated by the motor210and an external force EF1 acting in a direction that promotes opening of the tailgate118.FIG.4Bis a schematic view illustrating an opening direction of rotation MD1of the first portion298aof the clutch298connected to the reduction drive212, and a direction CS1in which the second portion298bof the clutch298would slip if the applied force EF1 becomes excessive. In this case, if the clutch298slips excessively in the direction of CS1, the tailgate118may travel from the fully closed position118cto the fully open position118zafter fewer motor rotation edges than expected, because the tailgate is moving downwardly faster than the motor210is attempting to lower it.

A similar situation is shown inFIGS.7A-7B.FIG.7Ais a schematic side view of a rear portion of the vehicle100showing fully closed (118c), fully open (118z), and intermediate positions of a tailgate118. The tailgate is acted on by a closing force MF4 generated by the motor210and an external force EF4 acting in a direction that promotes closing of the tailgate118.FIG.4Bis a schematic view illustrating a closing direction of rotation MD2of a first portion298aof the clutch298connected to the reduction drive212, and a direction CS2in which the second portion298bof the clutch298would slip if the applied force EF4 becomes excessive. In this case, if the clutch slips excessively in the direction of CS2, the tailgate118may travel from the fully open position118zto the fully closed position118cafter fewer motor rotation edges than expected, because the tailgate is moving toward the closed position faster than the motor210is attempting to raise it.

A different possible situation is shown inFIGS.5A-5B.FIG.5Ais a schematic side view of a rear portion of the vehicle100showing fully closed (118c), fully open (118z), and intermediate positions of a tailgate118. The tailgate is acted on by an opening force MF2 generated by the motor210and an external force EF2 acting in a direction that opposes opening of the tailgate118.FIG.5Bis a schematic view illustrating an opening direction of rotation MD1of a first portion298aof the clutch298connected to the reduction drive212, and a direction CS2in which the second portion298bof the clutch298would slip if the applied force EF2 becomes excessive. In this case, if the clutch slips excessively in the direction of CS2, the tailgate118may fail to reach the desired fully open position, because the force EF2 and clutch slippage are great enough to prevent downward motion of the tailgate while the motor210is running. Thus, the motor may reach the expected number of motor rotation edges before the tailgate reaches the fully open position118z.

A similar situation is shown inFIGS.6A-6B.FIG.6Ais a schematic side view of a rear portion of a pickup showing fully closed (118c), fully open (118z), and intermediate positions of a tailgate118. The tailgate is acted on by a closing force MF3 generated by the motor210and an external force EF3 acting in a direction that opposes closing of the tailgate118.FIG.6Bis a schematic view illustrating a closing direction of rotation MD2of a first portion298aof the clutch298connected to the reduction drive212, and a direction CS1in which the second portion298bof the clutch298would slip if the applied force EF3 becomes excessive. In this case, if the clutch slips excessively in the direction of CS1, the tailgate118may fail to reach the desired fully closed position, because the force EF3 and clutch slippage are great enough to prevent upward or closing motion of the tailgate while the motor is running. Thus, the motor may reach the expected number of motor rotation edges before the tailgate reaches the fully closed position118c.

The “predetermined slip amount” for each of the above situations may be an amount of slip which causes an associated desynchronization of the screw and the reduction drive severe enough to prevent the desired position of the tailgate118from being reached during normal motorized operation. The “predetermined slip amount” for each condition may be determined analytically and/or experimentally for a given tailgate control system configuration.

In one or more arrangements, the tailgate control system must be reset by manually returning or “resetting” the tailgate118to the fully closed position before the tailgate can be operated again automatically.

In one operational mode, to enable manual resetting of the tailgate, the tailgate control module323may include instructions that, when executed by the processor(s)144, cause the processor(s)144to, simultaneously with or following generating the alert, control operation of the power tailgate system to power down the motor210. Controlling operation of the power tailgate system to “power down” the motor210may comprise controlling operation of the system to interrupt or prevent a flow of electrical current to the motor, to halt operation of the motor. A user may then manually rotate the tailgate118back to the fully closed condition. During this manual movement of the tailgate118, the clutch298may slip as previously described without backdriving the elements of the reduction drive212and motor210.

In particular arrangements, the tailgate control module323may include instructions that, when executed by the processor(s)144, cause the processor(s) to enable a user to select a motor “power-down” mode to be automatically implemented simultaneously with (or following) generation of the alert indicating a need for manual reset of the tailgate118. For example, the input system156may be configured to enable user selection of the “power-down” operation mode to be implemented by the tailgate control module323.

In one exemplary user-selectable “power-down” mode, the tailgate control module323may include instructions that, when executed by the processor(s)144cause the processor to, simultaneously with generation of the alert indicating a need for manual reset of the tailgate, automatically power down the motor210. In another exemplary user-selectable “power-down” mode, the tailgate control module323may include instructions that, when executed by the processor(s)144, cause the processor(s) to automatically power down the motor210after passage of a predetermined time period following generation of the alert indicating a need for manual reset of the tailgate118. In yet another exemplary user-selectable “power-down” mode, the tailgate control module323may include instructions that, when executed by the processor(s)144, cause the processor(s) to wait for the user to generate a separate motor “power-down” command following generation of the alert indicating a need for manual reset of the tailgate118. The tailgate control module323may also include instructions that, when executed by the processor(s)144, cause the processor(s) to, upon receipt of the user-generated “power-down” command, power down the motor210.

In one or more arrangements, manual reset of the tailgate118may involve disengaging the motor210from the tailgate118. To this end, the tailgate control module323may include instructions to automatically disengage the motor210and the tailgate118to enable manual reset of the tailgate118, determine when the manual reset of the tailgate is complete and, responsive to the manual reset of the tailgate being complete, automatically engage the motor210with the tailgate118.

The motor210and the tailgate118may be considered “engaged” when the motor and the tailgate118are operably connected by elements interposed between the motor and the tailgate, to enable torque to be transmitted by the motor to the tailgate118and from the tailgate to the motor. The motor210and the tailgate118may be considered “disengaged” when the motor and the tailgate are not operably connected by elements interposed between the motor and the tailgate, such that torque cannot be transmitted by the motor to the tailgate and torque cannot be transmitted from the tailgate to the motor. Manual reset of the tailgate118may also include manually manipulating the tailgate to the fully closed position of the tailgate so that the latches may engage and to activate switches or sensors (such as tailgate position sensor379, as shown inFIG.1A) indicating that the tailgate is in the fully closed position and is thus reset. The tailgate control module323may determine that manual reset is complete when the motor210and the tailgate118are re-engaged after closing of the tailgate118.

In one or more arrangements, disengagement of the tailgate118from the motor210may be implemented by interposing one or more automatically actuatable clutches into the torque transmission chain between the motor and the tailgate. For example, in one or more particular arrangements, disengagement and re-engagement of the motor210with the tailgate118may be implemented using a clutch structured to be automatically actuatable responsive to commands from the tailgate control module323as executed by the processor(s)144. The automatically actuatable clutch may be engaged/disengaged by an actuator (e.g., an electric or hydraulic actuator) controllable by instructions stored in the tailgate control module323and executable by the processor(s)144.

In particular arrangements, the clutch may be an electrically-actuatable clutch (such as an electromagnetic clutch). However, any suitable clutch may be used provided it is controllable by the tailgate control module323to operably engage and disengage the motor from the tailgate for purposes of enabling and preventing raising and lowering of the tailgate by operation of the motor as described herein.

One example1298of an electrically-actuatable clutch is shown schematically inFIG.8.FIG.8is a schematic side cross-sectional view (similar to the view shown inFIG.2) of another embodiment422of the tailgate actuator. Elements of actuator422which are the same as elements used in actuator122have been given the same reference numerals.

As seen fromFIG.8, actuator422may be substantially similar to actuator122, the main difference being the incorporation of a second, automatically actuatable clutch1298interposed between reduction drive212and slip clutch298. In one or more arrangements, the automatically actuatable clutch1298is an electromagnetic clutch configured to operate in a manner opposite that of a conventional electromagnetic clutch. That is, the clutch1298may be configured to engage to enable transmission of torque through the clutch when the electromagnet is unenergized and to disengage (thereby preventing transmission of torque through the clutch) when a current is applied to energize the electromagnet. For example, the second clutch1298may include a first portion1298arigidly attached to a portion of the reduction drive212that would otherwise be directly operably connected to the screw214to transmit torque to the screw (and to receive torque from the screw). “Rigidly attached” as used herein means that the first portion1298aand the portion of the reduction drive are attached so as to rotate together, by the same angular amount, when one or the other of the first portion1298aand the portion of the reduction drive is rotated. The second clutch1298may also include a second portion1298brigidly attached to the first portion298aof the previously described slip clutch298. The second clutch1298is also structured so that the first portion1298amay be non-slippably engaged with the second portion1298bfor transmission of torque between the motor210and the screw214(i.e., the clutch may be structured so that torque is transmitted between the motor210and the screw214by the clutch1298without slip when the first portion1298ais in direct physical contact with the second portion1298b). The clutch1298may also be structured so that the first portion1298amay be disengaged (i.e., separated from) second portion1298bso that the first portion cannot transmit torque to (or receive torque from) the second portion1298b.

In a particular arrangement, the clutch1298may be an electromagnetic clutch in which first portion1298amay be moved out of contact with (or disengaged from) second portion1298bby energizing an electromagnet (not shown) incorporated into the clutch. Activation of the electromagnet may magnetically attract the clutch first portion1298ato draw the first portion away from the second portion1298b. To re-engage the clutch first and second portions1298a,1298band enable transmission of torque through the clutch1298, the clutch may be provided with suitable spring members (not shown) which bias the first portion1298ainto contact with the second portion1298b. The spring forces generated should be sufficient to maintain non-slip contact between the second clutch first and second portions1298a,1298bduring operation of the motor210to raise and lower the tailgate118. Also, the attractive force generated by the electromagnet(s) should be sufficient to overcome the forces exerted on the clutch first portion1298aby the biasing springs.

In operation, when the clutch1298is energized responsive to instructions from the tailgate control module323, clutch first portion1298ais moved out of contact with clutch second portion1298b, thereby disengaging the motor210and the screw214to prevent torque transmission between motor210and screw214. The tailgate118may then be manually reset to the closed position without moving elements of the reduction drive212and motor210. After it is determined that the tailgate has been manually reset, the clutch1298may be de-energized to “unpower” the clutch, thereby deactivating the electromagnet(s). This allows the clutch biasing springs to move the clutch first portion1298aback into contact with clutch second portion, thereby enabling transmission of torque between the motor210and the screw214.

In the embodiment shown inFIG.8, the slip clutch298may operate as previously described herein with respect toFIGS.2and4A-7B.

Another example2298of an automatically-actuatable clutch is shown inFIGS.9A and9B.FIG.9Ais a schematic side cross-sectional view (similar to the view shown inFIG.2) of another embodiment922of the tailgate actuator, showing an integrated clutch2298in an engaged condition.FIG.9Bis a view of a portion of the actuator922shown inFIG.9A, showing the integrated clutch2298in a disengaged condition. Elements of actuator922which are the same as elements used in actuator122have been given the same reference numerals. As seen fromFIG.9A, actuator922may be substantially similar to actuator122, the main difference being that the slippable clutch function is incorporated into an integrated clutch2298interposed between reduction drive212and the screw214. The clutch2298is “integrated” in that it is structured to perform the function of the slip clutch298previously described and also to enable selective engagement/disengagement as seen in the previously described automatically actuatable clutch1298.

In one or more arrangements, the integrated clutch2298may be operably connected to the motor210and the tailgate118. Generally, the automatically actuatable clutch2298may include a first portion operably connected to the motor210and a second portion operably connected to the tailgate118. The clutch2298may be structured to provide non-slippable torque transmission between the motor210and the clutch first portion. The clutch2298also including a mechanism structured to be engageable to enable slippable torque transmission between the motor210and the clutch second portion and disengageable to prevent torque transmission between the motor210and the clutch second portion. Then, automatically disengaging the motor from the tailgate may be performed by operating the clutch2298to disengage the mechanism to prevent torque transmission between the motor210and the clutch second portion.

For example, in the particular embodiment shown inFIGS.9A-9B, integrated clutch2298may include a first portion or housing2298arigidly attached to a portion of the reduction drive212that would otherwise be directly operably connected to the screw214to transmit torque to the screw (and to receive torque from the screw). “Rigidly attached” means that the housing2298aand the portion of the reduction drive are attached so as to rotate together, by the same angular amount, when one or the other of the housing2298aand the portion of the reduction drive are rotated. The housing2298amay define a cavity2298sstructured for positioning a movable clutch plate2298ptherein. The clutch first portion2298amay be operably connected to the motor210via attachment to the reduction gear.

The integrated clutch2298may also include a second portion2298brigidly attached to the screw214. The clutch second portion2298bmay be operably connected to the tailgate118via the attachment to the screw214.

Clutch plate2298pmay be movably positioned inside the housing2298a. The clutch plate2298pmay be structured so as to rotate together with the integrated clutch first portion2298a. The clutch plate2298pmay also be movable to engage the clutch second portion2298bto enable slippable transmission of torque between the motor210and the tailgate118during rotation of the integrated clutch first portion2298a. The clutch plate2298pmay also be movable to disengage from the integrated clutch second portion2298bto prevent transmission of torque between the motor210and the tailgate118. In one particular arrangement, the clutch plate2298pmay be movable within the housing cavity2298salong splines2298kformed along interior surfaces of the housing. The splines2298kmay engage associated spline-receiving notches (not shown) formed along the outer edges of the clutch plate2298p. The splines may enable movement of the clutch plate2298pwithin the housing2298ain directions toward and away from the clutch second portion2298b, while also ensuring that the clutch plate always rotates together with the integrated clutch first portion2298a.

In a particular arrangement, the clutch2298may be an electromagnetic clutch in which the clutch plate2289pmay be moved out of contact with (or disengaged from) clutch second portion2298bby energizing an electromagnet (not shown) incorporated into the clutch. Activation of the electromagnet may magnetically attract the clutch plate2298pto draw the clutch plate away from the clutch second portion2298b. To re-engage the clutch plate2298pwith the clutch second portion2298bto enable transmission of torque through the clutch2298, the clutch may be provided with suitable spring members2298wwhich bias the clutch plate2298pinto contact with the clutch second portion2298bfor slippable torque transmission. The spring forces generated should be sufficient to maintain the desired slippable contact between the clutch plate2298pand the clutch second portion2298b. Also, the attractive force generated by the electromagnet(s) should be sufficient to overcome the forces exerted on the clutch plate2298pby the biasing springs.

Referring toFIGS.9A and9B, in operation, when the clutch2298is energized responsive to instructions from the tailgate control module323, clutch plate2298pis moved out of contact (FIG.9A) with clutch second portion2298b, thereby preventing torque transmission between motor210and screw214and disengaging the motor210and the screw214. The tailgate118may then be manually reset to the closed position without moving elements of the reduction drive212and motor210. After it is determined that the tailgate118has been manually reset, the clutch2298may be de-energized responsive to instructions from the tailgate control module323to “unpower” the clutch (FIG.9A), thereby deactivating the electromagnet(s). This allows the clutch biasing springs2298wto move the clutch plate2298pback into contact with clutch second portion2298b, thereby enabling transmission of torque between the motor210and the screw214.

In one or more arrangements, the tailgate control module323may include instructions that when executed by the processor(s)144cause the processor(s)144to control operation of the motor210to attempt to lower the tailgate118from a fully closed position to a fully open position. The tailgate control module323may include instructions to determine if the tailgate118is in the fully open position. The tailgate control module323may include instructions to, responsive to a determination that the tailgate118is in the fully open position, discontinue operation of the motor210to attempt to lower the tailgate. The tailgate control module323may include instructions to determine a difference between a number of motor rotation edges (EEO) expected to occur during operation of the motor to lower the tailgate118from the fully closed position to the fully open position, and a number of motor rotation edges (EA1) that occurred during operation of the motor to attempt to lower the tailgate118from the fully closed position to the fully open position. The tailgate control module323may include instructions to, if the difference between EEO and EA1 is greater than or equal to a predetermined tolerance value TEEO assigned to EEO, determine that the clutch298slipped by at least the predetermined slip amount.

In certain arrangements described herein, the actual number of motor rotation edges detected during operation of the motor210to attempt to lower or raise the tailgate118may be used in determining the amount of clutch slippage. The tailgate control module323may include instructions to record the actual number of motor rotation edges detected during operation of the motor210to attempt to lower or raise the tailgate118. This actual number of motor rotation edges may be stored in a memory.

In certain arrangements described herein, the tailgate118may be subjected to an external force during at least a portion of operation of the motor210to attempt to lower the tailgate, and the externally-applied force may act in a direction that promotes lowering of the tailgate118. In such cases, slippage of the clutch298by at least the predetermined slip amount may be produced by the externally-applied force.

In one or more arrangements, the tailgate control module323may include instructions that when executed by the processor(s)144cause the processor(s)144to control operation of the motor210to attempt to lower the tailgate118from a fully closed position to a fully open position. The tailgate control module323may include instructions to determine if a number (EEO) of motor rotation edges expected to occur during operation of the motor to lower the tailgate118from the fully closed position to the fully open position has been reached. The tailgate control module323may include instructions to, responsive to a determination that the number of motor rotation edges expected to occur during operation of the motor to lower the tailgate118from the fully closed position to the fully open position has been reached, determine if the tailgate has reached the fully open position. The tailgate control module323may include instructions to, responsive to a determination that the tailgate118has not reached the fully open position, determine that the clutch298slipped by at least the predetermined slip amount.

The tailgate control module323may include instructions that when executed by the processor(s)144cause the processor(s)144to control operation of the motor210to attempt to lower the tailgate118from a fully closed position to a fully open position. The tailgate control module323may also include instructions to determine if the tailgate118has returned to the fully closed position during operation of the motor210to attempt to lower the tailgate from the fully closed position to the fully open position. The tailgate control module323may also include instructions to, responsive to a determination that the tailgate118returned to the fully closed position, determine that the clutch298slipped by at least the predetermined slip amount (i.e., if the external force was severe enough to return the tailgate to the fully closed position after the motor had moved the tailgate out of the fully closed position in an attempt to open the tailgate, it may be determined that the clutch slippage was severe enough to require manual reset of the tailgate system).

In certain arrangements described herein, the tailgate118may be subjected to an externally-applied force during at least a portion of operation of the motor210to attempt to lower the tailgate, and the externally-applied force may act in a direction that opposes lowering of the tailgate118. In such cases, slippage of the clutch298by at least the predetermined slip amount may be produced by the externally-applied force.

In one or more arrangements, the tailgate control module323may include instructions that when executed by the processor(s)144cause the processor(s)144to control operation of the motor210to attempt to raise the tailgate118from a fully open position to a fully closed position. The tailgate control module323may also include instructions to determine if a number EEC of motor rotation edges expected to occur during operation of the motor to raise the tailgate118from the fully open position to the fully closed position has been reached. The tailgate control module323may also include instructions to, responsive to a determination that the number of motor rotation edges expected to occur during operation of the motor to raise the tailgate118from the fully open position to the fully closed position has been reached, determine if the tailgate has reached the fully closed position. The tailgate control module323may also include instructions to, responsive to a determination that the tailgate118has not reached the fully closed position, determine that the clutch298slipped by at least the predetermined slip amount.

The tailgate control module323may include instructions that when executed by the processor(s)144cause the processor(s)144to control operation of the motor210to attempt to raise the tailgate118from a fully open position to a fully closed position. The tailgate control module323may also include instructions to determine if the tailgate118returned to the fully open position during operation of the motor210to attempt to raise the tailgate from the fully open position to the fully closed position. The tailgate control module323may also include instructions to, responsive to a determination that the tailgate118has returned to the fully open position, determine that the clutch298slipped by at least the predetermined slip amount (i.e., if the external force was severe enough to return the tailgate to the fully open position after the motor has moved the tailgate out of the fully open position in an attempt to close the tailgate, it may be determined that the clutch slippage was severe enough to require manual reset of the system).

In certain arrangements described herein, the tailgate118may be subjected to an externally-applied force during at least a portion of operation of the motor210to attempt to raise the tailgate, and the externally-applied force may act in a direction that opposes raising of the tailgate118. In such cases, slippage of the clutch298by at least the predetermined slip amount may be produced by the externally-applied force.

In one or more arrangements, the tailgate control module323may include instructions that when executed by the processor(s)144cause the processor(s)144to control operation of the motor210to attempt to raise the tailgate118from a fully open position to a fully closed position. The tailgate control module323may also include instructions to, during operation of the motor210to attempt to raise the tailgate118, determine if the tailgate is currently in a fully closed position. The tailgate control module323may also include instructions to, responsive to a determination that tailgate118is currently in the fully closed position, discontinue operation of the motor210to attempt to raise the tailgate. The tailgate control module323may also include instructions to determine a difference between a number (EEC) of motor rotation edges expected to occur during operation of the motor210to raise of the tailgate118from the fully open position to the fully closed position, and a number (EA4) of motor rotation edges that occurred during operation of the motor to attempt to raise the tailgate from the fully open position to the fully closed position. The tailgate control module323may also include instructions to, if the difference is greater than or equal to a predetermined tolerance value, determine that the clutch298slipped by at least the predetermined slip amount.

The tailgate control module323may include instructions that when executed by the processor(s)144cause the processor(s)144to determine when a backdrive condition is occurring in the motor210responsive to application of an externally-applied force to the tailgate118when the tailgate is in a fully open position, and when the externally-applied force is acting so as to promote raising of the tailgate. The tailgate control module323may also include instructions to, responsive to an occurrence of a backdrive condition in the motor when the tailgate118is in the fully open position, control operation of the motor to attempt to raise the tailgate. The tailgate control module may be configured to interpret the occurrence of a backdrive condition when the tailgate is fully open as an intention of the user to automatically raise the tailgate.

The tailgate control module323may include instructions that when executed by the processor(s)144cause the processor(s)144to control operation of the motor210to attempt to raise the tailgate118from a fully open position to a half-latched position. This may be in response to a command from a user to raise the tailgate118to the half-latched position. The tailgate control module323may also include instructions to, during operation of the motor210to attempt to raise the tailgate, determine if the tailgate is currently in the half-latched position. The tailgate control module323may also include instructions to, responsive to a determination that the tailgate118is currently in the half-latched position, determine if the tailgate has been in the half-latched position for at least a time equal to a predetermined time period. The tailgate control module323may also include instructions to, responsive to a determination that the tailgate118has been in the half-latched position for at least a time equal to a predetermined time period, determine a difference between a number (EEH) of motor rotation edges expected to occur during raising of the tailgate118from the fully open position to the half-latched position, and a number (EEA) of motor rotation edges that occurred during operation of the motor210to attempt raise the tailgate from the fully open position to the half-latched position. The tailgate control module323may also include instructions to, if the difference is greater than or equal to a predetermined tolerance value, determine that the clutch298lipped by at least the predetermined slip amount.

In certain arrangements described herein, the tailgate118may be subjected to an externally-applied force during at least a portion of operation of the motor210to attempt to raise the tailgate, and the externally-applied force may act in a direction that promotes raising of the tailgate118. In such cases, slippage of the clutch298by at least the predetermined slip amount may be produced by the externally-applied force.

The processor(s)144, the tailgate control module323, and the memory146can be operably connected to communicate with each other and with the other elements of the vehicle, including various vehicle systems140and/or individual components thereof.

Referring again toFIG.1A, a sensor fusion algorithm325may be an algorithm (or a computing device storing an algorithm) configured to accept data from the sensor system142as an input. The data may include, for example, data representing information sensed at the sensors of the sensor system142. The sensor fusion algorithm325may include or be configured to be executed using, for instance, a Kalman filter, Bayesian network, or one or more other algorithm. The sensor fusion algorithm325may provide various assessments based on the data from sensor system142. Depending upon the embodiment, the assessments may include evaluations of evaluations of specific situations and/or evaluations of possible impacts based on the particular situation. Other assessments are possible. For example, the sensor fusion algorithm325may evaluate information from the vehicle sensors, vehicle systems and other information from outside the vehicle (such as GPS information) to determine whether a received tailgate opening command is remotely generated or locally generated (for example, from within the vehicle or by actuating a switch or button located on an exterior of the vehicle).

As noted above, the vehicle100can include the sensor system142. The sensor system142can include one or more sensors. “Sensor” means any device, component and/or system that can detect, and/or sense something. The one or more sensors can be configured to detect, and/or sense in real-time. As used herein, the term “real-time” means a level of processing responsiveness that a user or system senses as sufficiently immediate for a particular process or determination to be made, or that enables the processor to keep up with some external process. The sensor system142is operable to detect information about the vehicle100. In arrangements in which the sensor system142includes a plurality of sensors, the sensors can work independently from each other. Alternatively, two or more of the sensors can work in combination with each other. In such case, the two or more sensors can form a sensor network. The sensor system142and/or the one or more sensors can be operably connected to the processor(s)144, the data store(s)327, and/or other element(s) of the vehicle100(including any of the elements shown inFIG.1A).

The sensor system142can include any suitable type of sensor. Various examples of different types of sensors will be described herein. However, it will be understood that the embodiments are not limited to the particular sensors described. Various examples of sensors of the sensor system142are described herein. However, it will be understood that the embodiments are not limited to the particular sensors described. The sensor system142may include any sensors suitable for and/or required to perform any of the data acquisition and/or vehicle control operations contemplated herein.

Sensors of sensor system142may be communicably coupled to the various systems and components of the vehicle100. The sensors may be operably connected to the vehicle wireless communications interface383, as shown inFIG.1A, for transmission of information to a cloud or other storage facility or for vehicle-to-vehicle (V2V) or vehicle-to-everything (V2X) communications. The sensors may also be operably connected to other vehicle systems and components, such as data stores327and processor(s)144, for controlling the tailgate118and other portions of the vehicle100. The existence of any predetermined conditions described herein may be calculated or otherwise determined using sensor data.

Along with the sensors shown inFIG.1A, the vehicle100may include one or more additional tailgate-related sensors such as latch sensors (not shown), tailgate orientation or position sensors, and other sensors required for the performance of the vehicle control operations described herein. Relatedly, the sensor system142may be operable to detect, for example, the movement of the tailgate118, the operation of the latches134, requests to automatically open the tailgate118, requests to automatically close the tailgate118, and the operational statuses of one, some or all of the vehicle systems140, including the energy system150, the tailgate actuator122and the latch actuators154, and the values of tailgate-related parameters and the existence and non-existence of various predetermined conditions.

The sensor system142may include one or more tailgate position sensors379configured to detect an opening status of the tailgate (i.e., whether the tailgate is closed, latched, partially open, fully open, etc.) and/or a rotational orientation or position of the tailgate (i.e., the degree to which the tailgate is open or closed at any given point in time).

The sensor system142may include a Hall-effect sensor371located in the actuator122and operably connected to the motor210. The Hall-effect sensor371may be configured to detect rotations of the motor armature. In one or more arrangements, rotations of the motor armature may be counted and expressed in terms of motor rotation “edges” as represented by portions of signal pulses produced by the Hall-effect sensor371operably connected to the motor210. The Hall-effect sensor371may be configured to detect rotations of the armature and produce signal or pulse corresponding to an armature rotation (or a fraction of an armature rotation). In one or more arrangements, the resulting signal may be in the form of one or more a square-wave(s)398as shown inFIG.3. Referring toFIG.3, in certain arrangements, the Hall-effect sensor371may be configured to generate two square-wave pulses (such as398aand398b) per armature rotation. Two square-wave pulses may include four edges E1-E4. Thus, in this arrangement, four motor rotation edges may be produced for each complete rotation of the armature. A digital counter (not shown) may be operably connected to the Hall-effect sensor for counting an actual number of motor rotation edges detected during operation of the motor210to raise and lower the tailgate118responsive to various user commands and instructions generated by the tailgate control module323. Counter values for a current operation of the tailgate may be stored in a memory for purposes of comparison with expected motor rotation edge values as described herein. The counter may be configured to automatically reset to “zero” during a manual reset of the tailgate as described herein.

The vehicle100can include one or more vehicle systems, collectively designated140. Various examples of the one or more vehicle systems140are shown inFIG.1A. However, the vehicle100can include more, fewer, or different vehicle systems. It should be appreciated that although particular vehicle systems are separately defined, each or any of the systems or portions thereof may be combined or segregated via hardware and/or software within the vehicle100.

The vehicle systems140may be operable to perform vehicle functions. On behalf of the vehicle system140to which it belongs, each vehicle element is operable to perform, in whole or in part, any combination of vehicle functions with which the vehicle system140is associated. The vehicle systems140may be communicatively connected with the memory146, the tailgate actuator(s)122, processor(s)144, and any other elements and systems of the vehicle100as needed to perform the tailgate control functions described herein.

The tailgate118, latch assemblies130, actuator(s)122, tailgate control module323, and any sensors providing information relating to tailgate operations may collectively define a power tailgate system of the vehicle100. In addition, the vehicle systems140may include an energy system150. Elements of the power tailgate system may be connected to the energy system150. The energy system150may be operable to perform one or more energy functions, including but not limited to storing and otherwise handling electrical energy. Elements of the power tailgate system may be operable to perform one or more tailgate control functions using electrical energy from the energy system150, including but not limited to automatically opening the tailgate118and automatically closing the tailgate118.

The vehicle100can include an input system156. An “input system” includes any device, component, system, element or arrangement or groups thereof that enable information/data to be input into a machine. For example, the input system156may include a keypad, a touch screen or other interactive display, a voice-recognition system and/or any other device or system which facilitates communications between a user and the vehicle. The input system156can receive wireless input from a vehicle occupant (e.g., a driver or a passenger) or a user located remotely from the vehicle100. For example, the input system may enable a user to input tailgate control commands to the tailgate control module.

The vehicle100can also include an output system158. An “output system” includes any device, component, or arrangement or groups thereof that enable information/data to be presented to a vehicle occupant (e.g., a driver, a vehicle passenger, etc.) or a remote user. For example, the output system may be operable to issue tactile, sound and visual outputs that may be sensed by users. The output system may enable a user to receive alerts or other information relating to the position, speed, and other operating parameters of the tailgate.

The vehicle wireless communications interface383may be configured to enable and/or facilitate communication between the components and systems of the vehicle and entities (such as cloud facilities, cellular and other mobile communications devices, other vehicles, remote servers, pedestrians, etc.) exterior of the vehicle. Wireless communications interface383may be configured to facilitate, establish, maintain, and end wireless V2V and V2X communications with any extra-vehicular entity, for example other connectibly-configured vehicles and connected vehicles, pedestrians, servers and entities located in the cloud, edge servers, and other information sources and entities. User-initiated commands such as wireless tailgate opening commands may be received and other types of information may be transmitted and received via the communications interface383. If required, wireless communications interface383may incorporate or be in communication with any network interfaces needed to communicate with any extra-vehicular entities and/or networks.

FIGS.4C,5C,6C, and7Care flow diagrams illustrating operation of the tailgate control system in accordance with embodiments described herein. Operations of the slippable clutches disclosed herein will be described in terms of clutch298ofFIGS.2and8. However, it will be understood that this description is also applicable to operation of the slippable portions of clutch2298ofFIGS.9A and9B(i.e., clutch plate2298pand clutch second portion2298bwhen these elements are engaged with each other).

FIG.4Cis a flow diagram showing one exemplary mode of operation of the tailgate control system in a situation such as that depicted inFIGS.4A-4B. In block402, a user may manually activate an automatic tailgate (TG) opening function by actuating a switch or button. In block406, the tailgate control module323may control operation of the motor210to attempt to open the tailgate118by exerting an opening force MF1 on the tailgate118. The motor210may be controlled to generate the expected number of rotations EEO needed to lower the tailgate118from the fully closed position to the fully open position.

At some point during operation of the motor210to attempt to lower the tailgate118, the externally applied force EF1 may also act on the tailgate118so as to urge it in the opening direction. The applied force EF1 may or may not cause the clutch298to slip. If the clutch slips, it will slip in a direction CS1which is the same as the direction of the reduction drive output. The applied force EF1 and any resulting clutch slippage may be short term/temporary, intermittent, or constant.

At some point during operation of the motor210to lower the tailgate118, a jam condition may be detected. Referring to block408, if a jam condition is detected during operation of the motor to open the tailgate118, the control module323may stop power operation of the tailgate. Otherwise, the control module323may (in block409) determine if the tailgate118is in the fully open position.

A jam or pinch condition may occur when an obstacle in the path of motion of the tailgate118impedes or prevents the tailgate from moving toward the desired position. Criteria are known for jam or pinch detection in a tailgate or door attempting to open or close. For example, the current drawn by the motor210may be monitored for a current spike resulting from the motor “working harder” to move the tailgate118past an obstacle preventing the desired motion. Additional or alternative jam detection criteria may also be used.

If the tailgate118is not in the fully open position, the control module323may (in block406) continue operating the motor to attampt to to lower the tailgate. However, if the tailgate118is in the fully open position, the control module323may (in block411) stop power operation of the tailgate to lower the tailgate. Also, if the clutch298slipped due to the external load while the tailgate118was being lowered, the tailgate will reach the fully open position before the expected number of motor rotation edges has been detected. In this case, attainment of the fully open position may be read as a jam condition, because the motor210will not know that the clutch has slipped or by how much, and the motor210will continue to try to lower the tailgate118past the fully open position until the expected number of motor rotation edges have been completed. To detect this condition, the control module may (in block412) determine if (EEO-EA1) > = TEEO (i.e., if the difference between the number of motor rotation edges EEO expected to occur during lowering of the tailgate from the fully closed position to the fully open position, and the actual number of motor rotation edges EA1 detected during the period when the tailgate moved from fully closed to fully open, is equal to or greater than the tolerance TEEO assigned to EEO).

If the difference is below the tolerance TEEO, the control module may (block416) conclude that there was little or no clutch slip during the movement and that the system operated normally. Thus no manual reset would be needed. However, if the difference is equal to or greater than the tolerance, the control module may (block416) conclude that the amount of clutch slippage met or exceeded the predetermined slip amount, and generate a signal indicating a need for manual reset. As stated previously, the presence of the tailgate in the fully open position may be detected by a suitable switch or sensor.

FIG.5Cis a flow diagram showing one exemplary mode of operation of the tailgate control system in a situation such as that depicted inFIGS.5A-5B.

In block502, a user may manually activate an automatic tailgate (TG) opening function by actuating a switch or button. In block504, the tailgate control module323may control operation of the motor210to attempt to open the tailgate118by exerting an opening force MF2 on the tailgate118. The motor210may be controlled to generate the expected number of rotations EEO needed to lower the tailgate from the fully closed position to the fully open position.

At some point during operation of the motor to attempt to lower the tailgate, the externally applied force EF2 may also act on the tailgate118so as to urge it in the closing direction. The applied force EF2 may or may not cause the clutch298to slip. If the clutch slips, it will slip in a direction CS2opposite the direction of rotation MD1of the reduction drive output. The applied force EF2 and any resulting clutch slippage may be short term/temporary, intermittent, or constant.

At some point during operation of the motor to lower the tailgate, a jam condition may be detected. Referring to block506, if a jam condition is detected during operation of the motor to open the tailgate118, the control module323may (in block510, as shown inFIG.5C) stop power operation of the tailgate. Also, at some point during operation of the motor210to lower the tailgate118, a backdrive condition may be detected in the motor, causing reverse operation of the motor. This may be detectible using the Hall effect sensor371. If (in block508) reverse operation of the motor is detected, the control module may (in block510) stop power operation of the tailgate118. If reverse operation of the motor is not detected, the control module may (in block512, as shown inFIG.5C) determine if the tailgate118has returned to the fully closed position. if the tailgate returns to the fully closed position following a command to open the tailgate, the external load EF2 may have been sufficient to cause the tailgate118to close all the way instead of opening. This may indicate a condition where the clutch was constantly slipping while the tailgate was being forced in the closing direction until the tailgate was closed. The presence of the tailgate in the fully closed position may be detected by a suitable latch switch or sensor. If this condition is detected in block512despite that fact that the tailgate was instructured to open. the control module may (in block510) halt power operation and (in block514, as shown inFIG.5C) assume that the amount of clutch slippage met or exceeded the predetermined slip amount, and signal the need for manual reset.

Returning to block512, if the tailgate118has not returned to the fully closed position, the control module323may (in block516) determine if the expected number EEO of motor rotation edges have been detected since the motor210began operation to lower the tailgate. If the expected number EEO of motor rotation edges has not been detected, control may return to block504to continue operation of the motor to open the tailgate118in the manner just described. However, if the expected number EEO of motor rotation edges has been detected, the control module may (in block517) stop power operation of the tailgate. The EEO for purposes of this determination may include all numbers of motor rotation edges within the range (EEO ± TEEO).

In addition, the control module may determine (in block518, as shown inFIG.5C) if the tailgate118is in the fully open position. If the tailgate is in the fully open position after the expected number of motor rotation edges have been implemented, the control module323may (block520) conclude that there was little or no clutch slip during the movement and that the system operated normally. Thus no manual reset would be needed. However, if the tailgate118is not in the fully open position after the expected number of motor rotation edges have been implemented, the control module may (block514) conclude that the amount of clutch slippage met or exceeded the predetermined slip amount, and generate a signal indicating a need for manual reset.

FIG.6Cis a flow diagram showing one exemplary mode of operation of the tailgate control system in a situation such as that depicted inFIGS.6A-6B.

In block602, a user may manually activate an automatic tailgate (TG) closing function by actuating a switch or button. In block604, the tailgate control module323may control operation of the motor210to attempt to close the tailgate118by exerting an closing force MF3 on the tailgate118. The motor210may be controlled to generate the expected number of rotations EEC needed to raise the tailgate from the fully open position to the fully closed position.

At some point during operation of the motor210to attempt to raise the tailgate118, the externally applied force EF3 may also act on the tailgate118so as to urge it in the opening direction. The applied force EF3 may or may not cause the clutch298to slip. If the clutch slips, it will slip in a direction CS1opposite the direction of rotation MD2of the reduction drive output. The applied force EF3 and any resulting clutch slippage may be short term/temporary, intermittent, or constant.

At some point during operation of the motor to lower the tailgate, a jam condition may be detected. Referring to block608, if a jam condition is detected during operation of the motor210to close the tailgate118, the control module323may (in block610) stop power operation of the tailgate. Also, at some point during operation of the motor210to raise the tailgate, a backdrive condition may be detected in the motor, causing reverse operation of the motor. This may be detectible using the Hall-effect sensor. If (in block612) reverse operation of the motor210is detected, the control module323may (in block610) stop power operation of the tailgate.

If reverse operation of the motor210is not detected, the control module may (in block613) determine if the tailgate118has returned to the fully open position. if the tailgate returns to the fully open position following a command to close, the external load EF3 may have been sufficient to cause the tailgate to open all the way instead of closing. This may indicate a condition where the clutch298was constantly slipping while the tailgate118was being forced in the opening direction until the tailgate was fully open. The presence of the tailgate118in the fully open position may be detected by a suitable latch switch or sensor. If this condition is detected in block613despite that fact that the tailgate was instructured to open. The control module323may (in block610) halt power operation and (in block620) assume that the amount of clutch slippage met or exceeded the predetermined slip amount, and signal the need for manual reset.

Returning to block613, if the tailgate has not returned to the fully open position, the control module323may (in block614) determine if the expected number EEC of motor rotation edges have been detected since the motor210began operation to raise the tailgate. If the expected number EEC of motor rotation edges has not been detected, control may return to block604to continue operation of the motor to open the tailgate118in the manner just described. However, if the expected number EEC of motor rotation edges has been detected, the control module may (in block617) stop power operation of the tailgate. The EEC for purposes of this determination may include all numbers of motor rotation edges within the range (EEC ± TEEC).

In addition, the control module may determine (in block616) if the tailgate118is in the fully closed position. If the tailgate118is in the fully closed position after the expected number of motor rotation edges have been implemented, the control module323may (block618) conclude that there was little or no clutch slip during the movement and that the system operated normally. Thus no manual reset would be needed. However, if the tailgate118is not in the fully open position after the expected number of motor rotation edges have been implemented, the control module may (block620) conclude that the amount of clutch slippage met or exceeded the predetermined slip amount, and generate a signal indicating a need for manual reset.

FIG.7Cis a flow diagram showing one exemplary mode of operation of the tailgate control system in a situation such as that depicted inFIGS.7A-7B. In this operational mode, automatic closing of the tailgate118may be initiated in either of two ways. In a first aspect (block702), the system may be configured to start to automatically close the tailgate responsive to an externally-applied closing force exerted by a human user. The backdrive produced by the external force may be interpreted by the system as a user desire to close the tailgate. In another aspect (block704), a user may manually activate an automatic tailgate closing function by actuating a switch or button as previously described. Responsive to either of these inputs, the control module323may (block706) control the motor210to generate the expected number of motor rotation edges EEC associated with raising the tailgate from the fully open position to the fully closed position.

If a jam condition is detected (block708), the control module323may (in block710) stop power operation of the tailgate118.

In one or more arrangements, the vehicle may have a half-latch capability for holding the tailgate118in a half-latched position, and a full-latch capability for holding the tailgate in the fully-closed position. A user may desire to close the tailgate to the half-latched position. This may be reflected in the user selecting a command to automatically close the tailgate118to the half-latched position or by the user exerting an external force EF4 to move the tailgate to this position, then removing the external force.

If the tailgate118reaches the half-latched position (block712) and remains in this position for at least a predetermined time period (block714), the control module323may assume that the user desires to leave the tailgate in the half-latched position. The control module323may then (in block716) compare the number of motor rotations EEH expected in moving the tailgate from the fully open position to the half-latched position, with the actual number of rotations EA4 detected by operation of the motor to move the tailgate118to the half-latched position. If the difference between these values is less than the tolerance TEEH, the control module323may assume (block718) that the tailgate118moved to the half-latched position with minimal/no slip of the clutch. Then, no manual reset of the system will be needed. However, if the calculated difference is greater than the tolerance TEEH (for example, the actual number of rotations required to move the tailgate to the half-latched position is markedly less than the expected number EEH), the control module323may assume that the clutch slip was equal to or greater than the predetermined slip amount due to application of the external load EF4 to the tailgate during movement of the tailgate from the fully open position to the half-latched position. In this case, the control module323may (in block726) signal the need for manual reset.

Returning to block714, if the tailgate118does not remain in the half-latched position for at least the predetermined time period, the control module323may assume that it is desired to move the tailgate to the fully-closed position. The control module323may then continue to operate the motor210to move the tailgate toward the fully-closed position unless a jam condition is detected in block720. If a jam condition is detected, the system may (block710) stop power operation of the tailgate.

During movement of the tailgate118between the fully-open position and the fully-closed position, the clutch298may also slip due to application of the external force EF4. The applied force EF4 may or may not cause the clutch to slip. If the clutch slips, it will slip in a direction CS2(FIG.7B) which is the same as the rotation direction MD2of the reduction drive output. The applied force EF4 and any resulting clutch slippage may be short term/temporary, intermittent, or constant.

If no jams are detected, the control module may continue to control operation of the motor210to close the tailgate118until (block722) the tailgate has reached the fully closed position. When the tailgate reaches the fully closed position, the control module323may (block728) stop power operation of the tailgate. The control module323may then (block724) compare the number of motor rotations edges EEC expected in moving the tailgate from the fully open position to the fully-closed position, with the actual number of motor rotation edges EA4 detected by the motor when the tailgate has arrived in the fully-closed position. If the difference between these values is less than the tolerance TEEC, the control module may assume (block718) that the tailgate was moved to the fully-closed position with minimal/no slip of the clutch. Then, no manual reset of the system will be needed. However, if the calculated difference is equal to or greater than the tolerance TEEC (for example, the actual number of rotations EA4 required to move the tailgate to fully-closed is markedly less than the expected number EEC), the control module323may assume that the clutch slip was equal to or greater than the predetermined slip amount due to application of the external load EF4 to the tailgate during movement of the tailgate from the fully open position to the fully closed position. In this case, the control module may (in block726) signal the need for manual reset.