Control on road slope during single pedal driving mode

Abstract

The invention provides control on a road grade during a single pedal driving mode. A vehicle includes: a power plant; an accelerator pedal; a sensor associated with the accelerator pedal and configured to output data indicative of an accelerator pedal position; and a controller. The controller is programmed to command a torque including a gravity cancellation component to the powerplant when the vehicle is on a non-flat road slope, where the torque is commanded such that the gravity cancellation component converges toward zero as the accelerator pedal position increases.

Description

Technical Field

[0001] The present disclosure relates to vehicle torque control that compensates for gravity. Background Art

[0002] Electrified vehicles, such as pure electric vehicles and hybrid electric vehicles, include at least one electric motor for propelling the vehicle. The motor is powered by a traction battery that supplies energy to the motor, which reduces the battery's state of charge (SOC). Many electrified vehicles are capable of regenerative braking to recharge the battery by converting mechanical power into electricity. Some electric vehicles offer single-pedal driving. Summary of the invention

[0003] According to one embodiment, a vehicle includes a powerplant and a controller. The controller is programmed to, in response to the vehicle being on an uphill grade, command a torque to the powerplant based on a driver-requested wheel torque plus a compensation torque to mitigate gravity drag associated with the uphill grade, wherein the compensation torque is derived from a drag torque corresponding to gravity drag minus a value based on the driver-requested torque.

[0004] According to another embodiment, a vehicle includes: a powerplant; an accelerator pedal; a sensor associated with the accelerator pedal and configured to output data indicative of an accelerator pedal position; and a controller. The controller is programmed to command a torque including a gravity-compensating component to the powerplant when the vehicle is on a non-flat road grade, wherein the torque is commanded such that the gravity-compensating component converges toward zero as the accelerator pedal position increases.

[0005] A method for counteracting gravity effects in a vehicle includes commanding a torque including a gravity counteracting component to a powerplant of the vehicle when the vehicle is on a non-flat road grade, wherein the torque is commanded such that the gravity counteracting component converges toward zero as accelerator pedal position increases. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 A schematic diagram of an example electrified vehicle is shown.

[0007] Figure 2 A schematic diagram showing the various torques present at the driven wheels of a vehicle.

[0008] Figure 3 is a flow chart of an algorithm for calculating the gravity drag torque associated with road grade.

[0009] Figure 4 is a flow chart of an algorithm for calculating commanded wheel torque taking into account the effects of gravity.

[0010] Figure 5 is a graph of wheel torque for a downhill grade.

[0011] Figure 6 is a graph of wheel torque for uphill slope. DETAILED DESCRIPTION

[0012] Embodiments of the present disclosure are described herein. However, it should be understood that the disclosed embodiments are merely examples, and other embodiments may take on various forms and alternative forms. The drawings are not necessarily drawn to scale; some features may be enlarged or minimized to show the details of a particular component. Therefore, the specific structural details and functional details disclosed herein are not to be interpreted as limiting, but only as a representative basis for teaching those skilled in the art to adopt the present invention in various ways. As will be understood by those of ordinary skill in the art, the various features shown and described with reference to any one of the drawings may be combined with the features shown in one or more other drawings to produce embodiments that are not explicitly shown or described. The combination of features shown provides representative embodiments for typical applications. However, for specific applications or embodiments, various combinations and modifications of features consistent with the teachings of the present disclosure may be desired.

[0013] Traditionally, the driver controls the vehicle speed by adjusting the accelerator pedal and the brake pedal. The driver depresses the accelerator pedal to travel faster and applies the brake pedal to slow down. Modern vehicles provide an opportunity for an alternative control called single-pedal driving (single-pedal driving mode), in which the vehicle can be controlled using only the accelerator pedal to accelerate and decelerate the vehicle. In the single-pedal driving mode, the driver commands the raw wheel torque required by the driver by actuating the accelerator pedal. Depending on the vehicle speed and the accelerator pedal position, the raw wheel torque required by the driver can be a positive or negative value. A positive value indicates a propulsion torque, while a negative value indicates a braking torque. (The negative torque required by the driver may also be referred to as a "target braking torque" in this article). The vehicle may use a powertrain system such as regenerative braking, a friction brake, or a combination of the two to provide the target braking torque.

[0014] The raw torque requested by the driver can be filtered and rate limited to smooth the acceleration and deceleration of the vehicle. Once filtered and rate limited, the torque can be referred to as the "commanded wheel torque". The rate limit constrains the step change between the wheel torque of the previous command and the wheel torque of the subsequent command. The vehicle can be programmed with multiple different filters and rate limits applied in different situations. For example, different filters and rate limits can be used depending on the vehicle speed, for example, a lower rate limit can be used when the vehicle is at a low speed, and a higher rate limit can be used when the vehicle is at a high speed. (A higher rate limit allows a larger step change than a lower rate limit.) Different filters and rate limits can also be used based on the mode of the vehicle. That is, when the vehicle is in a two-pedal driving mode, the vehicle may include a set of rate limits and filters, and when the vehicle is in a single-pedal driving mode, another set of rate limits and filters can be used.

[0015] The single-pedal driving mode can be configured to bring the vehicle to a complete stop when the driver has released the accelerator pedal without applying the brake pedal. The vehicle can be stopped using regenerative braking, friction braking, or both. Once the vehicle stops, the friction brakes can be applied to keep the vehicle stationary.

[0016] refer to Figure 1 , the electrified vehicle 20 is shown as a pure electric vehicle, but in other embodiments, the vehicle 20 may be a hybrid electric vehicle including an internal combustion engine, or a conventional electric vehicle including only an engine. The vehicle 20 is shown as two-wheel drive (such as front-wheel drive or rear-wheel drive), but in other embodiments may be all-wheel drive (AWD). The vehicle 20 may include a powertrain 24 that includes a power device, such as an electric motor 34, operable to accelerate (propel) and brake the vehicle 20.

[0017] The motor 34 is operably coupled to the driven wheels 30 and 32. A gearbox (not shown) may be included to change the gear ratio between the motor 34 and the wheels 30, 32. The gearbox may include one or more gear ratios. The motor may be one or more motors. The motor 34 can act as a motor to provide positive torque to propel the vehicle 20, and can act as a generator to provide negative torque to brake the vehicle, such as via regenerative braking. The motor 34 may be a permanent magnet three-phase alternating current (AC) electric motor or other suitable type.

[0018] The motor 34 is powered by one or more traction batteries, such as traction battery 36. The traction battery 36 stores energy that can be used by the motor 34. The traction battery 36 can provide a high voltage direct current (DC) output from one or more battery cell arrays (sometimes referred to as battery cell stacks) within the traction battery 36. The battery cell array includes one or more battery cells. The battery cell (such as a square, pouch, cylindrical, or any other type of unit) converts the stored chemical energy into electrical energy. The cell can include a housing, a positive electrode (cathode), and a negative electrode (anode). The electrolyte allows ions to move between the anode and the cathode during discharge, and then return during recharging. The terminals allow current to flow out of the cell for use by the vehicle 20. Different battery pack configurations can be used to meet various vehicle variables, including packaging constraints and power requirements. The battery cells can be thermally regulated using a thermal management system.

[0019] The traction battery 36 may be electrically connected to one or more power electronics modules via one or more contactors. The modules may be electrically connected to the motor 34 and may provide the ability to transfer electrical energy bidirectionally between the traction battery 36 and the motor 34. For example, the traction battery 36 may provide a DC voltage, while the motor 34 may require three-phase AC. The power electronics module may convert the DC voltage into a three-phase AC voltage as required by the motor. In a generator mode, which may be in the process of regenerative braking, the power electronics module may convert the three-phase AC voltage from the motor 34 acting as a generator into the DC voltage required by the traction battery 36.

[0020] The vehicle 20 includes one or more controllers 40 that are in electrical communication with a plurality of vehicle systems and are configured to coordinate the functions of the vehicle. The controller 40 may be a vehicle-based computing system that includes one or more controllers that communicate via a serial bus (e.g., a controller area network (CAN)) or via a dedicated electrical conduit. The controller 40 generally includes any number of microprocessors, ASICs, ICs, memories (e.g., FLASH, ROM, RAM, EPROM, and / or EEPROM) and software code to perform a series of operations in cooperation with each other. The controller 40 also includes predetermined data or a "lookup table" based on calculation and test data and stored in the memory. The controller 40 may communicate with other vehicle systems and controllers through one or more wired or wireless vehicle connections using a common bus protocol (e.g., CAN and LIN). Any reference to a "controller" used herein refers to one or more controllers. The controller 40 may include a battery energy control module (BECM) that operates at least a traction battery, a powertrain control module (PCM) that operates at least an electric motor, and a brake control control module that controls the brake system 38.

[0021] The controller communicates with various vehicle sensors and actuators via an input / output (I / O) interface, which may be implemented as a single integrated interface that provides various raw data or signal conditioning, processing and / or conversion, short circuit protection, etc. Alternatively, one or more dedicated hardware or firmware chips may be used to condition and process specific signals before supplying them to the CPU. Although not explicitly shown, one of ordinary skill in the art will recognize the various functions or components that may be controlled by the controller within each of the above-described subsystems.

[0022] Braking system 38 may be a hydraulic system, an electric system, or a combination of electric and hydraulic. Braking system 38 is a brake-by-wire system that uses a pedal sensor and actuator rather than a direct mechanical connection between the brake pedal and the master cylinder to engage the brakes. Alternatively, braking system 38 may be conventional.

[0023] The braking system 38 may include a master cylinder 47 that is in fluid communication with a plurality of friction brakes 42 located at each wheel. The master cylinder 47 may be actuated directly by the brake pedal or indirectly by the controller 40 based on data received from the accelerator pedal and the brake pedal sensor and other factors. Modern vehicles typically have disc brakes; however, other types of friction brakes are also available, such as drum brakes. In an example embodiment, each of the brakes 42 is in fluid communication with a valve body (not shown) via a brake line that is configured to deliver fluid pressure from the master cylinder 47 to the brake caliper of the brake 42. The valve body may include a plurality of valves that are configured to provide independent fluid pressure to each of the brakes 42 according to the ABS. The braking system 38 also includes associated wheel speed sensors 46, each of which is located at one of the wheels. Each sensor 46 is configured to output a wheel speed signal indicating the measured wheel speed to the controller 40.

[0024] The vehicle 20 is configured to brake using powertrain braking (e.g., regenerative braking), friction braking, or a combination thereof. The brake control module includes programming for aggregating the requested braking torque between the motor 34 and the friction brake 42. The requested braking torque may be based on driver input, such as the position of the brake pedal 44, or controlled by the controller 40 in a two-pedal driving mode. The aggregator may be programmed to use regenerative braking to decelerate the vehicle whenever possible, and to apply the friction brake 42 when necessary.

[0025] The vehicle 20 includes an accelerator pedal 45. The accelerator pedal 45 includes a travel range from a release position to a fully depressed position and an indeterminate position therebetween. The release position may be considered a zero percent position, and the fully depressed position may be considered a 100% position. Releasing the pedal may be referred to as lowering the accelerator pedal position, and applying the pedal may be referred to as increasing the accelerator pedal position. The accelerator pedal 45 includes an associated sensor (not shown) that senses the position of the pedal 45. The sensor is configured to output a pedal position signal indicating the sensed position of the pedal 45 (i.e., the accelerator pedal position) to the controller 40. The driver uses the accelerator pedal 45 to command the desired speed and torque of the vehicle. That is, the driver uses the accelerator pedal 45 to set the wheel torque (DDT) required by the driver. The torque required by the driver may be a positive value or a negative value. A positive value indicates a propulsion torque, while a negative value indicates a braking torque. (The negative torque required by the driver may also be referred to as a "target braking torque" in this article).

[0026] The controller 40 may be programmed to receive a pedal position signal and determine the driver's required torque based on the pedal position and other factors (such as vehicle speed). During the single-pedal driving mode, the accelerator pedal is used to set the target vehicle propulsion torque when the driver's required torque is positive, and the target braking torque when the driver's required torque is negative. The controller 40 may include a plurality of lookup tables or maps for determining the driver's required torque. These maps indicate the driver's required torque based on inputs such as accelerator pedal position, vehicle speed, and other factors. Different maps can be used for different driving modes. For example, one or more maps can be used when the vehicle is in a dual-pedal driving mode, and another map can be used when the vehicle is in a single-pedal driving mode. The map associated with the single-pedal driving mode may include a more aggressive driver-required negative torque value so that the vehicle is braked (powertrain, friction, or both) in response to the accelerator pedal being released, so that the brake pedal does not need to be applied in most cases.

[0027] The vehicle may include a human machine interface (HMI) for manually activating or deactivating the one-pedal driving mode. For example, the vehicle may include a touch screen head unit with various menus and settings. One of these settings may be to activate or deactivate the one-pedal driving. For example, one of the menus may include a capacitive touch screen selectable icon that may be selected to activate and deactivate the one-pedal driving mode.

[0028] Most roads follow the natural topography of the terrain, resulting in uphill and downhill sections that have a slope relative to flat ground. Uphill sections have a positive road slope, while downhill sections have a negative road slope. All things being equal, a vehicle will slow down when going uphill and will speed up due to gravity when going downhill. Therefore, a driver seeking to maintain a constant speed would traditionally increase the driver requested torque (i.e., further depress the accelerator pedal) when going uphill and reduce the driver requested torque (i.e., release the accelerator pedal) when going downhill.

[0029] The vehicle 20 may include one or more sensors 48 configured to determine the acceleration of the vehicle. For example, the sensors 48 may include a yaw rate sensor, a lateral acceleration sensor, a longitudinal acceleration sensor, a pitch sensor, and a roll sensor. The yaw rate sensor generates a yaw rate signal corresponding to the yaw rate of the vehicle. Using the yaw rate sensor, the yaw acceleration may also be determined. The lateral acceleration sensor outputs a lateral acceleration signal corresponding to the lateral acceleration of the vehicle. The longitudinal acceleration sensor generates a longitudinal acceleration signal corresponding to the longitudinal acceleration of the vehicle. The pitch sensor generates a signal corresponding to the pitch of the vehicle, and the roll sensor generates a signal corresponding to the roll of the vehicle. The various sensors communicate with the controller 40. In some embodiments, the yaw rate, lateral acceleration, longitudinal acceleration, pitch, roll, and other measurements may be measured by a single sensor.

[0030] The controller 40 can use one or more sensors 48 to determine the grade of the road, for example, flat, uphill or downhill. The road grade is determined by comparing the accelerometer-based longitudinal acceleration (which includes the effects of gravity) with the acceleration derived from the motor speed (which does not include the effects of gravity). The difference between these two accelerations produces an acceleration component due to gravity, which can be converted to an equivalent wheel torque by multiplying the vehicle mass and the tire radius.

[0031] The vehicle 20 is configured to help the driver maintain a constant speed by applying a compensating torque on top of the driver requested torque to account for gravity.

[0032] refer to Figure 2 , a vehicle 20 is shown stopped on an inclined surface and is shown having a number of forces and moments acting thereon. The surface has an inclination θ, which may also be referred to as a road grade. Here, the road grade is an uphill slope, which refers to an increase in elevation in the forward direction of travel. A downhill road grade refers to a decrease in elevation in the forward direction. The resultant torque T at the wheels of the vehicle is veh This can be calculated using Equation 1 as shown below:

[0033] T veh =Tacc +T brk -T rg (Equation 1)

[0034] Where T acc represents the propulsion torque provided by the powertrain, T brk is the braking torque provided by the vehicle braking system, and T rg It is the torque acting on the vehicle due to road grade or external forces. rg This can be referred to as the road grade torque. In the uphill example, T acc is depicted as a positive or clockwise moment, and T rg is depicted as a negative or counterclockwise torque. rg When pushing in the backward direction, T brk acts against the rotation of the wheel and will therefore act as a clockwise moment about the wheel, while when the vehicle is propelled in the forward direction, T brk will act as a counterclockwise moment about the wheels. Although each moment is shown as being about the front axle of the vehicle 20, one or more of these moments may act about both the front and rear axles. If the vehicle 20 is stationary, then T veh is equal to zero and the main road load is due to gravity. Equation 2 represents the torque used to calculate the road grade (T rg ) equation:

[0035] T rg =MgSin(θ)*R w (Equation 2)

[0036] where M is the mass of the vehicle; g is the acceleration due to gravity; θ is the inclination of the road; and R w is the radius of the driving wheel.

[0037] One use case for torque compensation is to prevent the vehicle from rolling back when it stops on a slope. Here, the controller 40 delays releasing the brake until the propulsion torque T acc Exceeding the road slope torque T rg The propulsion torque required to counteract the road grade and prevent rollback may be referred to as the grade compensation wheel torque. In the case of rollback mitigation, the grade compensation wheel torque is equal to the road grade torque, but in the opposite direction of rotation.

[0038] Another use case is to help the driver maintain a constant speed while moving by adding or subtracting torque (based on the grade of the road) to the torque requested by the driver (based primarily on the accelerator pedal position). The value of the grade compensation wheel torque can vary between full compensation and partial compensation. Full grade compensation refers to a torque that is equal to the effect of gravity. Partial compensation refers to a value that is less than full compensation and does not fully account for the effect of gravity.

[0039] Typically, when full grade compensation is applied on top of the driver requested torque, the driver can maintain a constant pedal position regardless of the road grade, and the vehicle will generally maintain a constant speed because the controller adds and subtracts torque as needed to compensate for gravity. One potential disadvantage of full grade compensation is that drivers of conventional vehicles may find it unintuitive when the vehicle does not decelerate when entering an uphill grade and does not accelerate when entering a downhill grade. This disadvantage can be mitigated by applying only partial grade compensation, so that the vehicle experiences some acceleration and deceleration expected based on the road grade change. Partial grade compensation can reduce driver effort and promote speed consistency by supplying some but not all of the torque required to mitigate the effects of gravity, so that fewer accelerator pedal changes are required. When partial grade compensation is applied, the vehicle will still experience some acceleration / deceleration in response to the road grade, providing the driver with a more traditional feel than full compensation.

[0040] The control logic or functions performed by the controller 40 may be represented by a flowchart or similar diagram in one or more of the accompanying drawings. These drawings provide representative control strategies and / or logic that may be implemented using one or more processing strategies (such as event-driven, interrupt-driven, multi-tasking, multi-threading, etc.). Thus, the various steps or functions shown may be performed in the order shown, may be performed in parallel, or may be omitted in some cases. Although not always explicitly shown, one of ordinary skill in the art will recognize that one or more of the steps or functions shown may be repeatedly performed, depending on the specific processing strategy used. Similarly, the processing order is not necessarily required to achieve the features and advantages described herein, but is provided for ease of illustration and description. The control logic may be implemented primarily in software executed by a microprocessor-based vehicle, engine and / or powertrain controller (such as controller 40). Of course, depending on the specific application, the control logic may be implemented in software, hardware, or a combination of software and hardware in one or more controllers. When implemented in software, the control logic may be provided in one or more computer-readable storage devices or media, which store data representing codes or instructions executed by a computer to control a vehicle or a vehicle subsystem. The computer-readable storage device or medium may include one or more of a number of known physical devices that utilize electrical, magnetic, and / or optical storage to hold executable instructions and associated calibration information, operating variables, and the like.

[0041] Figure 360 is a flow chart of an algorithm for calculating the full grade compensation torque. At operation 62, the controller 40 determines the vehicle acceleration without gravity. One method for performing this calculation is to measure the longitudinal vehicle acceleration with an accelerometer (e.g., sensor 48). Alternatively, the vehicle acceleration without gravity can be determined by estimating the actual total torque applied at the wheels by the powertrain, converting it to an equivalent force applied to the vehicle, and then converting this force to vehicle acceleration by dividing by the vehicle mass.

[0042] The vehicle speed 64 is received at box 66, which may be measured directly or calculated from the rotational speed of the motor 34, where the vehicle acceleration under gravity is calculated. At operation 66, the controller calculates the vehicle acceleration as the derivative of the vehicle speed, and the difference between the current vehicle speed and the previous vehicle speed is divided by the time increment between the times when the vehicle speed has been calculated or measured. Prior to calculating the derivative, the vehicle speed may be filtered with a low pass filter.

[0043] In operation 68, the controller 40 calculates the longitudinal gravity. The longitudinal gravity may be calculated using Equation 3, mass veh is the mass of the vehicle, and the acceleration with_G is the vehicle acceleration due to gravity, and acceleration without_G is the vehicle acceleration without gravity along the longitudinal vehicle axis.

[0044] Longitudinal gravity = mass veh x(acceleration with_G – Acceleration without_G )(Equation 3)

[0045] At operation 70 , the full grade compensation torque is calculated using Equation 4, for example.

[0046] Full Slope Compensation = - Longitudinal Gravity x Tire Radius (Equation 4)

[0047] Full grade compensation can be used as a starting point for calculating partial grade compensation. To provide a more intuitive driver feel, partial grade compensation can be based on driver requested torque.

[0048] Figure 4 A flow chart 100 for calculating the final wheel torque is shown. The controller 40 receives an accelerator pedal position 102 from a sensor associated with the accelerator pedal and receives a measured vehicle speed 104 at box 106. The controller calculates the driver requested torque at operation 106 based on the accelerator pedal position 102 and the vehicle speed 104 as discussed above. At operation 108, the controller calculates the full grade compensation, as Figure 3 As explained in .

[0049] The controller calculates a partial grade compensation torque at operation 110. The partial grade compensation torque may be based on full grade compensation that reduces the value of the torque and gain based on the driver request, as shown below in Equation 5.

[0050] Partial Slope Compensation = Full Slope Compensation - (Gain x DDT) (Equation 5)

[0051] At operation 112 , a final wheel torque command is calculated based on the driver requested torque of operation 106 and the partial grade compensation torque of operation 110 , as shown in Equation 6. The grade compensation torque (full or partial) may be referred to as the gravity offset component of the final torque command.

[0052] Final wheel torque = DDT + partial slope compensation (Equation 6)

[0053] Figure 5 and Figure 6 It shows how no grade compensation, full grade compensation and partial grade compensation affect the final wheel torque for an example driving situation. The graph shows wheel torque on the y-axis and accelerator pedal position (in percent) on the x-axis.

[0054] refer to Figure 5 , for simplicity, trace 120 shows the uncompensated wheel torque, which is a combination of the wheel torque requested by the driver and the gravity delivered to the wheels as additional wheel torque. Trace 122 shows the wheel torque when full grade compensation is applied, which is the wheel torque requested by the driver. Since this example is a downhill grade, the additional gravity wheel torque is positive, and the fully compensated wheel torque is less than the uncompensated torque. Trace 124 shows the wheel torque when partial grade compensation is applied. The partially compensated wheel torque 124 is between the uncompensated wheel torque 120 and the fully compensated torque 122. As shown in the graph, when the pedal position is 0%, the partially compensated torque 124 is consistent with the fully compensated torque 122, and converges toward the uncompensated torque 120 as the accelerator pedal is further depressed. That is, as the accelerator pedal position increases, the gravity offset component of the torque command converges toward zero.

[0055] Figure 6 The vehicle is shown on an uphill grade. In this example, the uncompensated wheel torque is shown by trace 130, the fully compensated wheel torque is shown by trace 132, and the partially compensated wheel torque is shown by trace 134. Since this example is uphill, the traces are roughly the opposite of the downhill example, with the fully compensated wheel torque 132 having the highest value and the uncompensated wheel torque 130 having the lowest value. Similar to Figure 5, the partially compensated torque has a value closer to the fully compensated torque at lower pedal positions and converges toward the uncompensated wheel torque 130 as the pedal is further depressed. That is, as the accelerator pedal position increases, the gravity-compensating component of the torque command converges toward zero.

[0056] Although exemplary embodiments are described above, these embodiments are not intended to describe all possible forms covered by the claims. The words used in the specification are descriptive words rather than restrictive words, and it should be understood that various changes can be made without departing from the spirit and scope of the present disclosure. As previously described, the features of various embodiments can be combined to form other embodiments of the present invention that may not be explicitly described or shown. Although various embodiments may have been described as providing advantages or being superior to other embodiments or prior art implementations in terms of one or more desired characteristics, it will be appreciated by those of ordinary skill in the art that one or more features or characteristics may be compromised to achieve the desired overall system properties, depending on the specific application and implementation. These properties may include, but are not limited to, strength, durability, marketability, appearance, packaging, size, maintainability, weight, manufacturability, ease of assembly, etc. For this reason, embodiments described as less desirable than other embodiments or prior art implementations in terms of one or more characteristics are within the scope of the present disclosure and may be desirable for specific applications.

[0057] According to the present invention, a vehicle is provided, the vehicle having: a power unit; and a controller, the controller being programmed to: in response to the vehicle being on an uphill slope, command a torque to the power unit based on a wheel torque requested by a driver plus a compensation torque to alleviate the gravity resistance associated with the uphill slope, wherein the compensation torque is derived from a resistance torque corresponding to the gravity resistance minus a value based on the torque requested by the driver.

[0058] According to one embodiment, the controller is further programmed to, in response to the vehicle being on a downhill grade, command another torque to the powerplant based on the driver-requested wheel torque minus another compensating torque to mitigate gravity drag associated with the downhill grade, wherein the another compensating torque is derived from a drag torque corresponding to gravity drag minus a value based on the driver-requested torque.

[0059] According to one embodiment, the compensation torque is equal to the resistance torque minus the driver requested torque multiplied by the gain.

[0060] According to one embodiment, the gain is a predetermined value.

[0061] According to one embodiment, the gain is based on the driver requested torque.

[0062] According to one embodiment, the vehicle further comprises an accelerometer.

[0063] According to one embodiment, the controller is further programmed to calculate the resistance torque based on data from the accelerometer.

[0064] According to one embodiment, the power device is an electric motor.

[0065] According to the present invention, a vehicle is provided, the vehicle having: a power unit; an accelerator pedal; a sensor associated with the accelerator pedal and configured to output data indicating the position of the accelerator pedal; and a controller programmed to command a torque including a gravity-compensating component to the power unit when the vehicle is on a non-flat road slope, wherein the torque is commanded so that the gravity-compensating component converges toward zero as the accelerator pedal position increases.

[0066] According to one embodiment, the gravity counteracting component is less than the gravity drag torque associated with the grade of the road.

[0067] According to one embodiment, the gravity counteracting component is based on the gravity resistance torque associated with the road grade and the driver requested wheel torque.

[0068] According to one embodiment, the gravity counteracting component is also based on a gain as a function of the accelerator pedal position.

[0069] According to one embodiment, the gravity counteracting component is based on the gravity resistance torque associated with the road grade and the driver requested wheel torque.

[0070] According to one embodiment, when the road slope is uphill, the gravity compensation component is a positive value, and when the road slope is downhill, the gravity compensation component is a negative value.

[0071] According to one embodiment, the vehicle further comprises an accelerometer, wherein the gravity compensation component is based on data from the accelerometer.

[0072] According to one embodiment, the power device is an electric motor.

[0073] According to the present invention, a method for counteracting the effects of gravity in a vehicle includes commanding a torque including a gravity counteracting component to a powerplant of the vehicle when the vehicle is on a non-flat road grade, wherein the torque is commanded such that the gravity counteracting component converges toward zero as accelerator pedal position increases.

[0074] According to one embodiment, the gravity counteracting component is less than the gravity drag torque associated with the grade of the road.

[0075] According to one embodiment, the gravity counteracting component is based on the gravity resistance torque associated with the road grade and the driver requested wheel torque.

[0076] According to one embodiment, the gravity counteracting component is also based on a gain as a function of the accelerator pedal position.

Claims

1. A vehicle comprising: Power plant; as well as a controller programmed to, in response to the vehicle being on an uphill grade, command a torque to the powerplant based on a driver requested wheel torque plus a compensation torque to mitigate a gravity drag associated with the uphill grade, wherein the compensation torque is derived from a drag torque corresponding to the gravity drag minus a value based on the driver requested torque.

2. The vehicle of claim 1 , wherein the controller is further programmed to, in response to the vehicle being on a downhill grade, command another torque to the powerplant based on the driver-requested wheel torque minus another compensating torque to mitigate gravity drag associated with the downhill grade, wherein the another compensating torque is derived from a drag torque corresponding to the gravity drag minus a value based on the driver-requested torque.

3. The vehicle of claim 1, wherein the compensation torque is equal to the resistance torque minus the driver-requested torque multiplied by a gain. The vehicle of claim 3 , wherein the gain is a predetermined value.

5. The vehicle of claim 3 wherein the gain is based on the driver requested torque.

6. The vehicle of claim 1 further comprising an accelerometer.

7. The vehicle of claim 6 wherein the controller is further programmed to calculate the drag torque based on data from the accelerometer.

8. The vehicle of claim 1, wherein the power plant is an electric motor.

9. A vehicle comprising: Power plant; Accelerator pedal; a sensor associated with the accelerator pedal and configured to output data indicative of an accelerator pedal position; as well as A controller is programmed to command a torque including a gravity cancelling component to the powerplant when the vehicle is on a non-flat road grade, wherein the torque is commanded such that the gravity cancelling component converges toward zero as the accelerator pedal position increases.

10. The vehicle of claim 9, wherein the gravity counteracting component is less than a gravity drag torque associated with the road grade.

11. The vehicle of claim 9, wherein the gravity counteracting component is based on a gravity resistance torque associated with the road grade and a driver requested wheel torque.

12. The vehicle of claim 11 wherein the gravity-compensating component is further based on a gain that is a function of the accelerator pedal position.

13. The vehicle of claim 9, wherein the gravity counteracting component is based on a gravity resistance torque associated with the road grade and a driver requested wheel torque.

14. The vehicle of claim 9, wherein the gravity counteracting component is a positive value when the road gradient is an uphill slope, and the gravity counteracting component is a negative value when the road gradient is a downhill slope.

15. The vehicle of claim 9 further comprising an accelerometer, wherein the gravity cancellation component is based on data from the accelerometer.

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