Patent Application
20180257649
This invention relates in general to vehicle speed control devices that regulate a user-selected vehicle speed level and, in particular, to speed control devices having an off-road speed maintaining capability.
This invention relates to a vehicle speed control system, that in one embodiment is configured with off-road performance features, that will allow the driver to travel at a set speed in a smooth, controlled manner on various unmaintained surfaces without requiring the driver to press the brake or accelerator pedal.
The invention concerns a vehicle speed control system for maintaining vehicle speed at a base target speed when the control system is activated by a vehicle driver, the system comprising:
a slope sensor for directly or indirectly determining the slope of the ground on which the vehicle is traveling;
a speed sensor for directly or indirectly determining the vehicle speed;
an engine controller for generating an engine torque request signal to operate an engine/drivetrain so as to control the vehicle speed at an engine target speed;
a brake controller for generating a brake request signal to operate vehicle brakes so as to control the vehicle speed at a brake target speed;
wherein when the vehicle is traveling uphill the brake target speed is greater that the engine target speed and the base target speed corresponds to the engine target speed; and
wherein the engine and brake controllers cooperate to maintain the vehicle speed at or near the base target speed.
Preferably, when the vehicle is traveling downhill the brake target speed is less than the engine target speed and the base target speed corresponds to the brake target speed. And, when the vehicle is at or near a level condition, the base target speed corresponds to the brake target speed. Optionally, the offset between the brake target speed and the engine target speed when the vehicle is traveling uphill increases with increasing steepness. As a further option, the engine controller may assume a passive operating state when the downhill slope exceeds a predetermined grade. The base target speed is selected by the vehicle driver.
As a separate and independent operating feature, the base target speed is a function of the slope on which the vehicle is traveling. As another separate and independent operating feature, the base target speed is a function of the steering angle.
Another separate and independent operating feature concerns that when the vehicle encounters an obstacle and the vehicle speed falls to or near zero, the system operates to increase engine torque so as to climb the obstacle; and wherein, at or near the time when the vehicle then begins to move (and the vehicle speed is still below the target speed), the vehicle braking is increased to preload the brake system prior to the vehicle speed reaching the target speed.
Another separate and independent operating feature concerns that when the vehicle it traveling uphill and the driver requests braking, the engine controller continues to generate the engine torque request signal until the driver's braking pressure reaches a predetermined level which is a function the steepness of the slope.
Another separate and independent operating feature includes a driver operable terrain switch for selecting an operating mode generally corresponding to a ground surface to be traversed (e.g., auto, rock, sand, mud, etc.); and wherein the engine controller operates at an adjustable engine gain for generating an engine torque request signal to operate an engine/drivetrain so as to control the vehicle speed at the target speed; wherein the brake controller operates at an adjustable braking gain for generating a brake request signal to operate vehicle brakes so as to control the vehicle speed at the target speed; and wherein at least one of the engine gain and braking gain is adjusted as a function of the terrain switch.
Another separate and independent operating feature concerns that when the vehicle speed is below the base target speed, the engine controller is operative to generate the engine torque request signal so as to increase engine torque to increase the vehicle speed to the base target speed; and wherein when the vehicle encounters an obstacle and the vehicle speed falls to or near zero, the system operates in a high torque mode for a certain time and then operates in reduced torque mode to at least temporarily reduce the engine torque.
Various aspects of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.
To facilitate this description, the following acronyms and definitions may be used:
In one embodiment, the vehicle cruise control system is a Select Speed Control Function (SSC) configured for use in on- and off-road conditions. When fully activated, the SSC is adapted to maintain speed of the vehicle at a speed selected by the vehicle driver. While at least a portion of the operating principles of SSC described herein are advantageously used for low speed control applications, such as speeds up to about 10 KPH, at least some of the operating principles described herein may be adapted for use in higher speed applications such as those found in, e.g., autonomous cruise control (ACC) systems. Preferably, the SSC system is adapted for use in a vehicle 10 of the type shown in
The EBCM 34, which includes Electronic Stability Control functionality, receives one or more of the following sensor inputs (sensors and inputs represented in part by block 44):
The TCM 38 provides the following functionality for the automatic transmission 14:
The CBC 42 operates to provide the following functionality:
Referring to
The EBCM, which is the driver of the SSC function, may output CAN messages, shown in Table 1 below, to various modules to modulate the engine torque, transmission gear, lamp handling, and the coupling of the rear differential to control the vehicle to the driver set target speed in a smooth manner while optimizing vehicle performance based on the driver selected terrain.
The central body control module (CBC) may output the following CAN messages, shown in Table 2 below, to the EBCM for use in the SSC subsystem.
The powertrain control module (PCM) may communicate the following CAN messages, shown in Table 3 below, to the EBCM to assist in the operation of the SSC function.
The PCM interface may optionally include a driver override function to determine when the driver is overriding the SSC torque request, that is internal to the PCM, and may be configured to set the SSC engine torque request to the “PASSIVE” state within the EBCM. A driver override CAN message may be sent out by the PCM when the driver is overriding the SSC torque request, similar to the architecture of a conventional Adaptive Cruise Control (ACC). This configuration may provide a more robust implementation of the driver override detection because the PCM is responsible for the torque signals and the accelerator pedal position. Thus, internal detection of the necessary inputs would be more robust due to internal fail safes on the signals. In addition, this embodiment may further improve the HMI interface to the driver by displaying a message that the driver is overriding the SSC system on the cluster. In addition, the EngTrqD_TTC signal will mirror the SSC-E torque request when the SSC function is actively modulating the engine torque. Also, the AccelPdlPosn signal will calculate the virtual pedal based on the SSC torque request during SSC control.
The transmission control module (TCM) may output the following CAN messages to the EBCM for use in the operation of the SSC. During SSC control, the transmission module may be configured as a slave to the EBCM in order to maintain the proper gearing to optimize the off road performance and smoothness of the SSC-E and SSC-B controller. As shown in Table 4 below, the transmission control module (TCM) may provide one or more of the following outputs.
The TCM may optionally default to a SSC specific transmission shift map when the SSC function is in the “ON” state. This configuration will allow the transmission to be calibrated specifically for SSC performance to eliminate the harshness associated with the handover between SSC and TCM control of the transmission during driver throttle override events. In addition, the speed target being limited as a function of grade is currently executed internally to the EBCM without informing the driver. Thus, as the vehicle climbs a steep hill, the speed target may be limited although the driver perceives that the PRNDL_DISP is the vehicle target speed. as a consequence, if the limited speed is slower than the driver desires, the driver may increase the target speed. In this embodiment, the EBCM may ignore the speed increase due to the internal grade speed limitation. As the driver crests the hill, the internal target speed will approach the driver selected target speed as a function of grade. This may result in the vehicle suddenly accelerating due to the change in target speed as a function of slope. As an alternative in this embodiment, a clean interface for this functionality may allow the EBCM to limit the PRNDL_DISP value based on the internal grade limitation and any other internal target speed limitations. A PRND_MAX messages can be implemented to overwrite the PRNDL_DISP gear as the target speed is limited by the EBCM. This will inform the driver of the internal modification of the target speed. Also, the PRNDL_DISP is normally not increased by the EBCM once the limitation condition no longer exists. In another variation of this embodiment, the driver may increase the target speed manually with paddles. This will improve the driver interface, and eliminate sudden accelerations as the driver crests a steep hill with a higher target speed than the internal grade limited target speed.
The drivetrain control module (DTCM) may be configured to output the following CAN messages, shown in Table 5 below, to the EBCM for use in the operation of the SSC function.
In operation, the Select Speed Control (SSC) function may be defined to have two states: ON and OFF. The states can be communicated to other vehicle modules through the use of the SelSpdSts message.
Under the CAN Protocol, when SelSpdSts=1, the SSC function is ON. The SSC function is ON when the function has been enabled by the driver and the Selec-Speed Brake Control Brake Controller (SSC-B) and Selec-Speed Control Engine Controller (SSC-E) are readily available to control their respective outputs to maintain the driver selected target speed. To the driver this state is represented by a continuously illuminated SSC lamp. It is noted that the SSC ON state does not need to contain any specific information on the status of individual SSC-E and SSC-B controllers. It may, however, be configured to convey that the SSC-B and SSC-E are available to the other modulates. In this embodiment, the SSC system may be configured with the following SSC Function Enabling Criteria in the ON state:
The SSC ON state may include a number sub-states, including SSC ON-Active Brake, SSC ON-Active Engine and SSC On-Passive.
The status of the SSC-B controller is determined to be active when the controller is actively requesting brake pressure. The status of the brake controller does not need to be directly conveyed via the CAN Bus during control with a unique message; however, the BrkTrq message outputs the estimated BrkTrq requested by the EBCM module. In this embodiment, the SSC-B controller may be active under one or more (including all) of the following conditions:
The status of the SSC-E controller is determined to be active when the SSC-E torque request (EngTrq_Rq_ESC) is greater than the driver requested torque (EngTrqD_TTC). The SSC ON-Active Engine state is present when the EngTrqMax_Rq_ESC is “1”. In this embodiment, the SSC-E controller may be activate under one or more (including all) of the following conditions:
The SSC system may have one or more (including all) portions set to a passive state, indicated as SSC ON-PASSIVE. In this state, the SSC function has been enabled by the driver, and neither, the SSC-B or the SSC-E is actively controlling the related subsystems. In this embodiment, the SSC-E and SSC-B controllers may be set to a passive state, while remaining available when one or more (including all) of the following conditions are present:
The status or indicator lamp is configured to signal to a driver to a condition of the operative SSC state. The lamp may be configured to indicate the SSC-ON State as follows: In the SSC ON-PASSIVE state, when the vehicle is over a predetermined speed (e.g., 20 mph) the lamp will flash for a certain time period (e.g., a maximum of 70 seconds) and then automatically disable. In addition, during this flash condition when the driver presses the HMI button or the vehicle speed exceeds a second hiher predetermined speed (e.g., 40 mph), the lamp will cease to be illuminated and SSC will transition to the SSC-OFF State. Other lamp signaling architectures may also be used to indicate the SSC state, if desired. In a specific embodiment, shown below in Table 6, the lamp signaling conditions may operate under one or more (including all) of the conditions indicated:
Under the CAN Protocol, when SelSpdSts=0, the SSC function is OFF. The SSC OFF state is defined as by the following conditions: the Selec-Speed function is not enabled, and the SSC-B and SSC-E controllers are inhibited from modulating their respective control outputs. To the driver, this state is represented by a non-illuminated SSC lamp. The SSC OFF state can be present in the following scenarios:
In addition, the transition from the SSC ON-ACTIVE to the SSC OFF state will occur in a controlled manner with a flashing lamp for a minimum of 2 seconds based on the following conditions:
The SSC function can transition from the SSC ON-ACTIVE to the SSC OFF state when the system is currently enabled and the HMI button is pressed with no flashing of the lamp. The SSC function can transition from the SSC ON-PASSIVE to the SSC OFF state when one or more of the following conditions are present:
As shown below in Table 7, the lamp actions associated with SCC OFF state transitions and conditions are presented.
Referring to
If a Hill Descent Control (HDC) feature is contained within the EBCM, the SSC system can be considered an extension of the HDC. Typically, the HDC system is designed to work on downhill slopes greater than a threshold, and it automatically modulates the brake pressure to control the vehicle speed to a driver set target speed while descending a hill. Gravity and idle torque, when the driveline is engaged, are the forces propelling the vehicle downhill. The HDC brake controller is referred to as SSC-B in the context of the Select Speed Control subsystem. The SSC system is composed of two concurrently running controllers that will modulate brake pressure and engine torque separately to maintain the driver selected target speed. The Select Speed Control engine controller is herein referred to as SSC-E. The SSC-E controller may be contained in the EBCM, and request the necessary torque for the vehicle to maintain the driver selected target speed in a slow, controlled manner when the vehicle is on a slope greater than a threshold. The control strategy at a constant base target speed is illustrated in
In addition to control of the brake and engine torque, the SSC function can use the gear selector (PRNDL) display to determine the driver set target speed with various internal modifications, control the maximum gear of the transmission, and the coupling status of the E-Locker when SSC is in the “ON” state.
The SSC-B controller can be configured to provide an HDC function that modulates the brake pressure to maintain the driver selected target speed as the vehicle travels down a slope steeper than a threshold. When the controller is configured as part of the SSC subsystem, the conditions may be modified to allow the SSC-B controller to modulate the brake pressure on all slopes. Thus, the SSC-B controller may be readily available once the driver has enabled the function through the HMI, independent of grade. The controller allows the driver to overlay a brake request and seamlessly take control of vehicle braking. In addition, any throttle override input by the driver will result in a ramp out of the brake pressure. In order to optimize performance of the SSC function, the SSC-B controller can use the information from a Terrain Select dial to modify control and/or calibrations for the driver selected surface. Any alternative or specific Hill Descent Control algorithm may be the foundation for the SSC-B.
Optionally, an SSC Rock Mode Brake Controller may be provided to address specific driving conditions or terrain. When a driver selects the Rock Mode, it may be assumed that the driver is on a surface such as a rock garden, or boulders. In order to minimize overshoots of the SSC control, an open loop term is added to the SSC-B controller to emulate two foot driving.
The SSC-E controller modulates the torque request to the engine control module. The activation of the SSC-E controller may be inhibited when the vehicle is traveling down a slope steeper than a threshold (e.g., 15%). On a slope steeper than the threshold, SSC-E is set to the passive state because gravity and idle torque forces are sufficient for the vehicle to maintain the target speed. Under these conditions, the vehicle functions only with the SSC-B controller. The SSC-E controller is a PI controller with an open loop term. The input to the SSC-E controller is the error between the target speed and the vehicle speed. The equation for the controller is:
Y=[Ki∫
□
e(t)dt+I_Hill(grade)]+Kpe(t)
The SSC-E controller is defined as being active when the SSC-E torque request is greater than the driver requested torque, the drive is not braking above a threshold, and the driveline is in a forward driven gear or reverse. This activation condition allows seamless driver torque overlay as the SSC-E controller transitions from the active to passive state. These transitions require the pre-loading of the I-term to maintain smooth control following a driver throttle or brake override of the system. To optimize the performance of the SSC function, it may be beneficial to permit the ability to gain the controller for each of the surfaces available on the Terrain Select dial.
Timeout logic of the SSC-E torque request may be implemented in order to protect the driveline from harm due to high torque requests by the SSC-E controller. Once an undesired situation due to the SSC-E torque request is determined, the SSC-E controller must reset to the torque request equivalent to the I Hill torque for 3 seconds; then the controller may reinitialize to the active state. The reset mechanism to the I Hill torque is beneficial because the limits can be reached on steep slopes and resetting to idle torque (the SSC-E Passive State) will result in significant roll back of the vehicle. The undesired torque requests are determine by the following checks:
The driver selected target speed is the base target speed that the SSC-E and SSC-B controllers control to; however, there are several influences that can modify the SSC-E and SSC-B target speed. Referring to Table 8 below, and
In another embodiment, a steering wheel angle is measured and inputted into the system. To prevent binding of the rear axle and crow hop, a high input of steering on a slope within an upper and lower limit will decrease the controller target speed to a maximum target speed. If the slope is outside the limits, no steering angle adjustment is performed on the base target speed. The input is the absolute value of the steering angle. Table 9 shows an embodiment of target speed limits as a function of steering angle and slope.
It will be appreciated that the specific relationship between the driver selected target speed, slope and steering angle can vary depending on the specific vehicle operating characteristics.
In addition to the internal adjustments on the control speed target, the target speed of the SSC-E and SSC-B controllers are offset, as shown in
Referring to
In one embodiment, the SSC function may be configured to request the maximum gear that the transmission can maintain during SSC ON control. The transmission may be configured to honor the request when the SSC function is enabled. Table 10, below, describes the implementation of the SSC gear request when the SSC function is enabled.
In a variation of this embodiment, the SSC performance may be configured as a Transmission Shift Map with shifting biased toward higher RPM values to be used during SSC-control. This may eliminate any harsh handover of control of target gear position between the transmission and the EBCM following a driver throttle override event. Referring to
The E-Locker differential configured for implementation of SSC is an electronic limited slip differential. When SSC is in the “ON” state, a coupling request is sent to the ELSD as a function of the absolute value of the steering angle when the estimated slope of the surface is below a threshold predetermined threshold indicative of a relatively flat terrain such as, e.g., +/−15%. If the estimated slope is above this threshold, the ELSD is requested to couple with the maximum force (100%). This slope threshold is implemented to prevent crow hop and binding on flat ground with a large steering input. Table 11 below shows examples of the relationship between steering angle, coupling request and the slope.
In a variation of this embodiment, the coupling request may only be allowed when the conditions are satisfied for SSC-E to enter the active state. The coupling request can also be tunable when the Select Terrain Dial is in the Rock position. This is done to maximize the performance of the vehicle by forcing the vehicle to remain a true 4-wheel-drive vehicle. Referring to
Another variation of this embodiment configured for the interface with the rear differential, is to allow the rear differential to arbitrate between the EBCM coupling request and their desired coupling request. The current implementation makes the rear differential a slave to the EBCM; thus, the coupling is only performed by request. The rear differential, which has history with off road performance, can be limited to honor the EBCM request only when it is greater than their internal request.
Another feature of the SCS control is shown in
In
Another feature of the SSC control is illustrated by
Another feature of the SSC system is illustrated in
As shown in
In summary, the Select-Speed Control function optimizes off-road vehicle performance by modulating the engine and brakes autonomously while allowing the driver to concentrate on the path of vehicle with only steering as an input. The system provides the capability to ascend or descend any obstacle that a typical driver could navigate within the limits of the vehicle.
The principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope. Additionally, each embodiment disclosed herein may be a stand alone component or combined with any or all of the other embodiments disclosed herein.
This application is a divisional patent application of U.S. patent application Ser. No. 14/650,456, filed Jun. 8, 2015 and published as U.S. 2015/0321671 A1 on Nov. 12, 2015. U.S. 2015/0321671 A1 is the National Phase of International Application No. PCT/US2013/73958, filed Dec. 9, 2013, which claims priority from U.S. Provisional Patent application No. 61/734,824, filed Dec. 7, 2012. The disclosures of these applications are incorporated herein by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61734824 | Dec 2012 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14650456 | Jun 2015 | US |
| Child | 15913298 | US |
