Torque control for vehicles with independent front and rear propulsion systems

Methods and systems for controlling torque for a front axle and a rear axle of a vehicle with independent front and rear propulsion systems are provided. A data unit is configured to obtain data for one or more parameters of a vehicle while the vehicle is being driven. A processor is coupled to the data unit, and is configured to provide torque to at least facilitate providing torque the front axle and the rear axle independently based on the one or more parameters.

TECHNICAL FIELD

The present disclosure generally relates to vehicles, and more particularly relates to methods and systems for controlling torque for multiple axles of vehicles.

BACKGROUND

Many vehicles today control torque for axles of the vehicle, for example by reducing or increasing torque to help compensate for vehicle understeer or vehicle oversteer and/or in various other situations. However, such existing techniques may sacrifice overall propulsion for the vehicle.

Accordingly, it is desirable to provide techniques for controlling torque for axles of vehicle, for example that maintain overall propulsion for the vehicle. Furthermore, other desirable features and characteristics of the present invention will be apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.

SUMMARY

In accordance with an exemplary embodiment, a method is provided. The method comprises obtaining data for one or more parameters of a vehicle while the vehicle is being driven, the vehicle having a front axle and a rear axle, and providing torque to the front axle and the rear axle independently based on the one or more parameters.

In accordance with an exemplary embodiment, a system is provided. The system comprises a data unit and a processor. The data unit is configured to obtain data for one or more parameters of a vehicle while the vehicle is being driven. The vehicle has a front axle and a rear axle. The processor is coupled to the data unit, and is configured to provide torque, or at least facilitate providing torque, to the front axle and the rear axle independently based on the one or more parameters.

In accordance with a further exemplary embodiment, a vehicle is provided. The vehicle comprises a body, a front axle, a rear axle, a data unit, and a processor. The front axle and rear axle are disposed within the body. The data unit is configured to obtain data for one or more vehicle parameters while the vehicle is being driven. The processor is disposed within the body, and is coupled to the data unit. The processor is configured to provide torque, or at least facilitate providing torque, to the front axle and the rear axle independently based on the one or more parameters.

DETAILED DESCRIPTION

FIG. 1illustrates a vehicle100, or automobile, according to an exemplary embodiment. As described in greater detail further below, the vehicle100includes a front axle102, a rear axle104along with a front propulsion system106, a rear propulsion system108, and a control system110that controls torque independently for the front and rear axles102,104using the front and rear propulsion systems106,108. In certain embodiments, the control system110comprises, is part of, and/or is coupled to one or more engine control systems (ECS) and/or safety systems for the vehicle100(such as for automatic braking, braking assist, steering assist, traction control, electronic stability control, lane departure warning, lane change awareness, and/or for one or more other active safety features), among other possible systems. As discussed further below, the control system110includes a sensor array112and a controller114that are used for controlling torque for the front and rear axles102,104.

As depicted inFIG. 1, the vehicle100also includes a chassis116, a body118, a plurality of wheels126, a steering system122, and a braking system124. The body118is arranged on the chassis116and substantially encloses the other components of the vehicle100. The body118and the chassis116may jointly form a frame. The wheels126are each rotationally coupled to the chassis116near a respective corner of the body118. In various embodiments the vehicle100may differ from that depicted inFIG. 1. For example, while four wheels126are depicted inFIG. 1, in certain embodiments the number of wheels126may vary.

In the exemplary embodiment illustrated inFIG. 1, the front propulsion system106and the rear propulsion system108are both mounted on the chassis116that drives the wheels126. The front propulsion system106moves the front axle102based on instructions provided by the control system110, and the rear propulsion system108moves the rear axle104based on instructions provided by the control system110, independent of one another. In various embodiments, the front and rear propulsion systems may comprise the same type or different types of propulsion systems, which may include, by way of example, batteries, electric motors, gas combustion engines, fuel cell engines, and/or various other types of propulsion systems.

The steering system122is mounted on the chassis116, and controls steering of the wheels126. The steering system122includes a steering wheel and a steering column (not depicted). The steering wheel receives inputs from a driver of the vehicle100. The steering column results in desired steering angles for the wheels126via drive shafts of the axles102,104based on the inputs from the driver.

The braking system124is mounted on the chassis116, and provides braking for the vehicle100. The braking system124receives inputs from the driver via a brake pedal (not depicted), and provides appropriate braking via brake units (also not depicted). The driver also provides inputs via an accelerator pedal (not depicted) as to a desired velocity or acceleration of the vehicle, as well as various other inputs for various vehicle devices and/or systems, such as one or more vehicle radios, other entertainment systems, environmental control systems, lighting units, navigation systems, and the like (also not depicted). Similar to the discussion above regarding possible variations for the vehicle100, in certain embodiments steering, braking, and/or acceleration can be commanded by a computer instead of by a driver.

The control system110is mounted on the chassis116. As discussed above, the control system110controls torque to the front and rear axles102,104via the front and rear propulsion systems106,108, respectively, and includes a sensor array112and a controller114.

The sensor array112includes various sensors (also referred to herein as sensor units) that are utilized to calculate a velocity of the vehicle using different techniques. In the depicted embodiments, the sensor array112includes one or more wheel sensors126, steering sensors128, and yaw sensors130. In one embodiment, the wheel sensors126measure wheel speeds and angles of one or more of the wheels126of the vehicle100. Also in one embodiment, the steering sensors128measure position and/or movement of a steering wheel of the steering system122of the vehicle100. In addition, in one embodiment, the yaw sensors130measure a yaw rate of the vehicle100. The measurements and information from the various sensors of the sensor array112are provided to the controller114for processing. In certain embodiments, the sensor array112may include one or more other sensors132such as, by way of example, one or more accelerometers (e.g., longitudinal and lateral accelerometers) and/or global positioning system (GPS) sensors and/or other sensors.

The controller114is coupled to the sensor array112. The controller114utilizes the various measurements and information from the sensors array112for providing torque independently for the front and rear axles102,104, using the front and rear propulsion system106,108, using various techniques. The controller114, along with the sensor array112, also provide additional functions, such as those discussed further below in connection with the flowcharts of the process200as depicted inFIGS. 2 and 3and discussed further below.

As depicted inFIG. 1, the controller114comprises a computer system. In certain embodiments, the controller114may also include one or more of the sensors of the sensor array112, one or more other devices and/or systems, and/or components thereof. In addition, it will be appreciated that the controller114may otherwise differ from the embodiment depicted inFIG. 1. For example, the controller114may be coupled to or may otherwise utilize one or more remote computer systems and/or other control systems, such as an electronic control system of the vehicle100.

In the depicted embodiment, the computer system of the controller114includes a processor134, a memory136, an interface138, a storage device140, and a bus142. The processor134performs the computation and control functions of the controller114, and may comprise any type of processor or multiple processors, single integrated circuits such as a microprocessor, or any suitable number of integrated circuit devices and/or circuit boards working in cooperation to accomplish the functions of a processing unit. During operation, the processor134executes one or more programs144contained within the memory136and, as such, controls the general operation of the controller114and the computer system of the controller114, generally in executing the processes described herein, such as the process200described further below in connection withFIGS. 2 and 3.

The memory136can be any type of suitable memory. For example, the memory136may include various types of dynamic random access memory (DRAM) such as SDRAM, the various types of static RAM (SRAM), and the various types of non-volatile memory (PROM, EPROM, and flash). In certain examples, the memory136is located on and/or co-located on the same computer chip as the processor134. In the depicted embodiment, the memory136stores the above-referenced program144along with one or more stored values146(e.g., any stored dynamic models, thresholds, and/or other values) for use in making the determinations.

The bus142serves to transmit programs, data, status and other information or signals between the various components of the computer system of the controller114. The interface138allows communication to the computer system of the controller114, for example from a system driver and/or another computer system, and can be implemented using any suitable method and apparatus. In one embodiment, the interface138obtains the various data from the sensors of the sensor array112. The interface138can include one or more network interfaces to communicate with other systems or components. The interface138may also include one or more network interfaces to communicate with technicians, and/or one or more storage interfaces to connect to storage apparatuses, such as the storage device140.

The storage device140can be any suitable type of storage apparatus, including direct access storage devices such as hard disk drives, flash systems, floppy disk drives and optical disk drives. In one exemplary embodiment, the storage device140comprises a program product from which memory136can receive a program144that executes one or more embodiments of one or more processes of the present disclosure, such as the steps of the process200(and any sub-processes thereof) described further below in connection withFIGS. 2 and 3. In another exemplary embodiment, the program product may be directly stored in and/or otherwise accessed by the memory136and/or a disk (e.g., disk148), such as that referenced below.

The bus142can be any suitable physical or logical means of connecting computer systems and components. This includes, but is not limited to, direct hard-wired connections, fiber optics, infrared and wireless bus technologies. During operation, the program144is stored in the memory136and executed by the processor134.

It will be appreciated that while this exemplary embodiment is described in the context of a fully functioning computer system, those skilled in the art will recognize that the mechanisms of the present disclosure are capable of being distributed as a program product with one or more types of non-transitory computer-readable signal bearing media used to store the program and the instructions thereof and carry out the distribution thereof, such as a non-transitory computer readable medium bearing the program and containing computer instructions stored therein for causing a computer processor (such as the processor134) to perform and execute the program. Such a program product may take a variety of forms, and the present disclosure applies equally regardless of the particular type of computer-readable signal bearing media used to carry out the distribution. Examples of signal bearing media include: recordable media such as floppy disks, hard drives, memory cards and optical disks, and transmission media such as digital and analog communication links. It will be appreciated that cloud-based storage and/or other techniques may also be utilized in certain embodiments. It will similarly be appreciated that the computer system of the controller114may also otherwise differ from the embodiment depicted inFIG. 1, for example in that the computer system of the controller114may be coupled to or may otherwise utilize one or more remote computer systems and/or other control systems.

While the control system110, the sensory array112, and the controller114are depicted as being part of the same system, it will be appreciated that in certain embodiments these features may comprise two or more systems. In addition, in various embodiments the control system110may comprise all or part of, and/or may be coupled to, various other vehicle devices and systems, such as, among others, propulsion systems106,108, steering system122, braking system124, and/or an engine control system for the vehicle100.

FIG. 2is a flowchart of a process200for controlling front and rear axles of a vehicle, in accordance with an exemplary embodiment. The process200can be implemented in connection with the vehicle100, including the control system110, ofFIG. 1, in accordance with an exemplary embodiment.

As depicted inFIG. 2, the process200is initiated at step202. Once the process is initiated, data is obtained (step203). In certain embodiments, the data includes measured and/or calculated parameter values that include a vehicle velocity as well as an actual slip angle (e.g., an estimated or actual slip angle), a desired slip angle, an actual yaw rate (e.g., an estimated or actual yaw rate), and a desired yaw rate for the vehicle. As referred to herein, (i) “slip angle” refers to angular difference between a direction in which the vehicle is pointed and a direction of travel of the vehicle; (ii) “actual slip angle” refers to an estimated, calculated, measured and/or actual slip angle for the vehicle (in certain embodiments, the actual slip angle is estimated using an on-board algorithm based on information from inertial measurement unit (IMU) sensors, vehicle motion, and driver inputs—in one such embodiment, the slip angle is estimated, nominally, by measuring a slip angle rate over time and integrating the slip angle rate); (iii) “desired slip angle” refers to a driver's intention for the slip angle for the vehicle (e.g. as determined a function of the vehicle suspension geometry and the vehicle velocity); (iv) “yaw rate” refers to an angular rotation of the vehicle over time; (v) “actual yaw rate” refers to a measured, calculated, and/or actual yaw rate for the vehicle (for example, as measured or determined using yaw rate sensors); and (vi) “desired yaw rate” refers to a driver's intention for the yaw rate for the vehicle (e.g. as determined as a function of a driver's engagement of a steering wheel of the vehicle and vehicle velocity).

In certain embodiments, background data for determining these parameter values is obtained in step203. In one embodiment, these values are obtained and/or determined by a data unit of the vehicle100ofFIG. 1, such as the various sensors of the sensor array112ofFIG. 1, and are provided to the controller114ofFIG. 1(and, specifically, the processor134thereof) for processing. In one exemplary embodiment, the vehicle velocity is obtained from wheel speed measurements from the wheel sensors126ofFIG. 1, the actual slip angle is estimated using an on-board algorithm based on information from inertial measurement unit (IMU) sensors, vehicle motion, and driver inputs, the actual yaw rate is determined from the yaw sensors130ofFIG. 1, the desired slip angle is determined as a function of the vehicle suspension geometry, driver inputs, and the vehicle velocity, and the desired yaw rate is determined from the vehicle velocity and steering sensors128ofFIG. 1and vehicle velocity.

A determination is made whether a vehicle velocity is greater than a first predetermined threshold (step204). In one embodiment, the vehicle velocity is obtained from step203. In addition, in one embodiment, the first predetermined threshold is stored in the memory136ofFIG. 1as one of the stored values146thereof. In one embodiment, this threshold may be approximately equal to five miles per hour (5 mph). However, this may vary in other embodiments. Also in one embodiment, the determination of step204is made by the processor134ofFIG. 1.

In certain embodiments, additional calculations are performed from the data of step203(step206). Specifically, in one embodiment, the actual slip angle, desired slip angle, and desired yaw rate are calculated in step206, to the extent that these values have not already been determined in step203. Also in one embodiment, the calculations of step206are performed by the processor134ofFIG. 1.

Determinations are as made as to whether (a) a rate of change of the actual slip angle over time is greater than or equal to a second predetermined threshold; and (b) the actual slip angle is greater than or equal to the desired slip angle (step208). In one embodiment, the rate of change of the slip angle over time is measured via one or more sensors. Also in one embodiment, the second predetermined threshold is stored in the memory136ofFIG. 1as one of the stored values146thereof. In one embodiment, the threshold may approximately be equal to two or three degrees per second (2 or 3 deg/sec); however, this may vary in other embodiments. Also in one embodiment, these determinations are made by the processor134ofFIG. 1.

If it is determined that both conditions of step208are satisfied; namely, (a) the rate of change of the actual slip angle over time is greater than or equal to the second predetermined threshold; and (b) the actual slip angle is greater than or equal to the desired slip angle, then the front axle torque and the rear axle torque are both reduced, based on the desired yaw rate and the measured rate (step210). In one embodiment, the torque adjustments are made based on instructions provided by the processor134ofFIG. 1to the front and rear propulsion systems106,108ofFIG. 1. The process then returns to the above-described step206in a new iteration.

With reference toFIG. 3, a flowchart is provided for step210(or sub-process210) of the process200, in accordance with an exemplary embodiment. In accordance with this embodiment, a determination is made as to whether a difference between the absolute value of the desired yaw rate minus the absolute value of the actual yaw rate is greater than a third predetermined threshold (step302). In one embodiment, the predetermined threshold of step302is stored in the memory136ofFIG. 1as one of the stored values146thereof. In one embodiment, the threshold may approximately be equal to five degrees per second (5 deg/sec); however, this may vary in other embodiments. Also in one embodiment, the determination of step302is made by the processor134ofFIG. 1.

If it is determined that the difference between the absolute value of the desired yaw rate minus the absolute value of the actual yaw rate is greater than the predetermined threshold of step302, then torque is reduced for both the front and rear axles such that the reduction in torque for the front axle is greater than the reduction in torque for the rear axle (step304). In one embodiment, the amount of torque to be reduced on both axles is determined in a dynamic manner rather than a fixed calibration number. In one such embodiment, this may be determined by a look-up table or a proportional integral derivative (PID) controller based on actual slip angle, desired slip angle, actual yaw rate, desired yaw rate, vehicle velocity, other vehicle motion status, or the like. In one embodiment, the torque adjustments are made based on instructions provided by the processor134ofFIG. 1to the front and rear propulsion systems106,108ofFIG. 1.

Conversely, if it is determined in step302that the difference between the absolute value of the desired yaw rate minus the absolute value of the actual yaw rate is less than or equal to the predetermined threshold of step302, then a determination is made as to whether a difference between the absolute value of the actual yaw rate minus the absolute value of the desired yaw rate is greater than a fourth predetermined threshold (step306). In one embodiment, the predetermined threshold of step306is stored in the memory136ofFIG. 1as one of the stored values146thereof. In one embodiment, the threshold of step306is less than the threshold of step302. In one such embodiment, the threshold of step306is approximately be equal to three degrees per second (3 deg/sec); however, this may vary in other embodiments. Also in one embodiment, the determination of step306is made by the processor134ofFIG. 1.

If it is determined that the difference between the absolute value of the actual yaw rate minus the absolute value of the desired yaw rate is greater than the predetermined threshold of step306, then torque is reduced to both the front and rear axles such that the reduction in torque for the rear axle is greater than the reduction in torque for the front axle (step308). In one embodiment, the amount of torque to be reduced on both axles is determined in a dynamic manner rather than a fixed calibration number. In one such embodiment, this may be determined by a look-up table or a proportional integral derivative (PID) controller based on actual slip actual angle, desired slip angle, actual yaw rate, desired yaw rate, vehicle velocity, other vehicle motion status, or the like. In one embodiment, the torque adjustments are made based on instructions provided by the processor134ofFIG. 1to the front and rear propulsion systems106,108ofFIG. 1. Also in one embodiment in which the values are calculated by a PID, as the error term decreases the command to modify torque also decreases. In one embodiment, the torque adjustments are made based on instructions provided by the processor134ofFIG. 1to the front and rear propulsion systems106,108ofFIG. 1.

Conversely, if it is determined in step306that the difference between the absolute value of the actual yaw rate minus the absolute value of the desired yaw rate is less than or equal to the predetermined threshold of step306, then torque is reduced to both the front and rear axles such that the reduction in torque for the rear axle is equal to the reduction in torque for the front axle (step310).

Returning to step208ofFIG. 2, if it is determined in step208that one or both conditions of step208are not satisfied; namely, that (a) the rate of change of the actual slip angle over time is less than the second predetermined threshold of step208and/or (b) the actual slip angle is less than the desired slip angle, then a further determination is made as to whether the rate of change of the actual slip angle over time is less than or equal to a fifth threshold; and (b) the actual slip angle is less than or equal to the desired slip angle (step212). In one embodiment, the predetermined threshold of step212is stored in the memory136ofFIG. 1as one of the stored values146thereof. In one embodiment, this threshold may be approximately equal to two or three degrees per second (2 or 3 deg/sec). However, this may vary in other embodiments. Also in one embodiment, the determinations of step212are made by the processor134ofFIG. 1.

If it is determined that both conditions of step212are satisfied; namely, (a) the rate of change of the actual slip angle over time is less than or equal to the predetermined threshold of step212; and (b) the actual slip angle is less than or equal to the desired slip angle, then the process proceeds to the above-described step210. Conversely, if is determined that either or both of these conditions of step212are not satisfied, then the process proceeds instead to step214, described below.

During step214, a determination is made as to whether a product of the desired yaw rate multiplied by the actual yaw rate is greater than or equal to zero. Alternatively stated, in one embodiment the determination of step214comprises a determination as to whether the desired yaw rate and the actual yaw rate have the same sign (i.e., positive or negative). In one embodiment, this determination is made by the processor134ofFIG. 1.

If it is determined in step214that the desired yaw rate and the actual yaw rate do not have the same sign, then torque to the front axle and the rear axle are both reduced (step216). In one embodiment, an equal amount of torque is reduced for both the front and rear axles. In one embodiment, the amount of torque to be reduced on both axles is determined in a dynamic manner rather than a fixed calibration number. In one such embodiment, this may be determined by a look-up table or a proportional integral derivative (PID) controller based on actual slip actual angle, desired slip angle, actual yaw rate, desired yaw rate, vehicle velocity, other vehicle motion status, or the like. Also in one embodiment, the torque adjustments are made based on instructions provided by the processor134ofFIG. 1to the front and rear propulsion systems106,108ofFIG. 1.

Conversely, if it is determined in step214that the desired yaw rate and the actual yaw rate have the same sign, then a determination is made as to whether a difference between the absolute value of the desired yaw rate and the absolute value of the actual yaw rate is greater than or equal to a sixth predetermined threshold (step218). In one embodiment, the predetermined threshold of step218is stored in the memory136ofFIG. 1as one of the stored values146thereof. In one embodiment, this threshold may be approximately equal to five degrees per second. However, this may vary in other embodiments. Also in one embodiment, the determination of step218is made by the processor134ofFIG. 1.

If it is determined in step218that the difference between the absolute value of the desired yaw rate and the absolute value of the actual yaw rate is greater than or equal to the predetermined threshold of step218, then torque to the front axle is reduced while torque to the rear axle is increased (step220). In one embodiment, the torque reduction for the front axle is equal to the torque increase for the rear axle, so that the overall balance of torque (and therefore the overall propulsion) for the vehicle remains the same. For example, in one embodiment, the amount of propulsion torque will be less than the driver-requested torque, but the distribution front/rear of the propulsion torque will remain the same (thus maintaining consistency of the propulsion torque with respect to the driver requested torque). In one embodiment, the torque adjustments are made based on instructions provided by the processor134ofFIG. 1to the front and rear propulsion systems106,108ofFIG. 1.

Conversely, if it is determined in step218that the difference between the absolute value of the desired yaw rate and the absolute value of the actual yaw rate is less than the predetermined threshold of step218, then a determination is made as to whether a difference between the absolute value of the actual yaw rate minus the absolute value of the desired yaw rate is greater than or equal to a seventh predetermined threshold (step222). In one embodiment, the predetermined threshold of step222is stored in the memory136ofFIG. 1as one of the stored values146thereof. In one embodiment, the threshold of step222may be the same as the threshold of step218. However, this may vary in other embodiments. Also in one embodiment, the determination of step222is made by the processor134ofFIG. 1.

If it is determined in step222that the difference between the absolute value of the actual yaw rate and the absolute value of the desired yaw rate is greater than or equal to the predetermined threshold of step222, then torque to the front axle is increased while torque to the rear axle is decreased (step224). In one embodiment, the torque increase for the front axle is equal to the torque reduction for the rear axle, so that the overall balance of torque (and therefore the overall propulsion) for the vehicle remains the same. For example, in one embodiment, the amount of propulsion torque will be less than the driver-requested torque, but the distribution front/rear of the propulsion torque will remain the same (thus maintaining consistency of the propulsion torque with respect to the driver requested torque). In one embodiment, the torque adjustments are made based on instructions provided by the processor134ofFIG. 1to the front and rear propulsion systems106,108ofFIG. 1.

Conversely, if it is determined in step222that the difference between the absolute value of the desired yaw rate and the absolute value of the actual yaw rate is less than the predetermined threshold of step222, then the process terminates (step226).

Accordingly, the process200controls torque independently for the front and rear axles of the vehicle, based on vehicle parameters that include vehicle velocity, desired slip angle, actual slip angle, actual yaw rate, and desired yaw rate for the vehicle. In addition, in certain embodiments, the process200provides for adjustments for certain vehicle conditions (e.g. vehicle oversteer and vehicle understeer) by adjusting torque on the front and rear axles independently in a manner that maintains overall propulsion for the vehicle100(or more specifically, that maintains the driver intended propulsion for the vehicle, as much as possible consistent with maintaining controllability, for example as described above in connection with steps220and224).

It will be appreciated that the disclosed methods, systems, and vehicles may vary from those depicted in the Figures and described herein. For example, the vehicle100, the control system110, and/or various components thereof may vary from that depicted inFIG. 1and described in connection therewith. In addition, it will be appreciated that certain steps of the process200may vary from that depicted inFIGS. 2 and 3and/or described above in connection therewith. It will similarly be appreciated that certain steps of the methods described above may occur simultaneously or in a different order than that depicted inFIGS. 2 and 3and/or described above in connection therewith.