AXLE TORQUE TILT ASSISTANCE

Abstract

A vehicle includes a system that performs a method for operating the vehicle. The system includes a road gradient sensor for measuring a road gradient of a section of roadway traveled by the vehicle, a speedometer for measuring vehicle speed, a power flow direction sensor for determining a direction of the vehicle's power flow, a pedal position sensor for measuring the pedal position, and a processor.The processor is configured to determine an upper axle torque limit for an engine of the vehicle based on road grade, vehicle speed, and direction of power flow, determine an axle torque request based on vehicle speed and pedal position, determine a limited axle torque request from the axle torque request and the upper axle torque limit, and control the vehicle by implementing the limited axle torque request in the vehicle.

Description

INTRODUCTION

[0001] The present disclosure relates to the operation of a vehicle and, more particularly, to a system and method for setting a torque limit for the torque applied to an axle of a vehicle.

[0002] Electric vehicles can be used in a variety of scenarios. In many scenarios, vehicles are used for long driving intervals with few stops. In other scenarios, some vehicles undergo short driving intervals with many stops and starts during their use. Such short driving interval scenarios include uses such as small vans or delivery trucks, use as a taxi, or ride-sharing vehicle. This type of starting and stopping causes wear and tear on the vehicle, such as tire wear, bearing wear, axle wear, and so on. To counteract these effects, a static limit is applied to the vehicle to restrict the torque that can be exerted on the vehicle's axles. However, if the vehicle is on an uphill or gradient road, this limit will affect the performance of the delivery vehicle.Therefore, it is desirable to provide a method for setting an axle torque limit to account for the effects of road gradient. SUMMARY

[0003] In an exemplary embodiment, a method for operating a vehicle is disclosed. The road gradient of a section of roadway traversed by the vehicle is measured using a vehicle-mounted road gradient sensor. Based on the road gradient, the vehicle speed, and the direction of the vehicle's power flow, an upper axle torque limit for an engine of the vehicle is determined. Based on the vehicle speed and a pedal position, an axle torque request is determined. A limited axle torque request is determined from the axle torque request and the upper axle torque limit. The vehicle is controlled by implementing the limited axle torque request in the vehicle.

[0004] In addition to one or more of the features described herein, the limited axle torque request is a minimum value of the axle torque request and the upper axle torque limit.

[0005] In addition to one or more of the features described herein, when the direction of power flow is in a forward gear, the method further comprises determining the upper axle torque limit to a first value when the road grade is within a zero grade range having an upper grade threshold, a second value greater than the first value when the road grade is a positive value greater than the upper grade threshold, or the first value when the road grade is negative.

[0006] In addition to one or more of the features described herein, when the direction of power flow is in a reverse gear, the method further comprises determining the upper axle torque limit to a first value when the road grade is within a zero grade range with a lower grade threshold, the first value when the road grade is positive, or a second value greater than the first value when the road grade is negative and less than the lower grade threshold.

[0007] In addition to one or more of the features described here, the upper axle torque limit increases with increasing road gradient when the vehicle is traveling uphill.

[0008] In addition to one or more of the features described herein, this further includes selecting a default value for road grade when a road grade measurement is invalid and / or a power flow direction is invalid.

[0009] In addition to one or more of the features described here, the road inclination sensor is an acceleration sensor.

[0010] In another exemplary embodiment, a system for operating a vehicle is disclosed. The system includes a road gradient sensor for measuring a road gradient of a road section traveled by the vehicle, a speedometer for measuring the vehicle speed, a power flow direction sensor for determining a direction of the vehicle's power flow, a pedal position sensor for measuring the pedal position, and a processor.The processor is configured to determine an upper axle torque limit for an engine of the vehicle based on road grade, vehicle speed, and direction of power flow, determine an axle torque request based on vehicle speed and pedal position, determine a limited axle torque request from the axle torque request and the upper axle torque limit, and control the vehicle by implementing the limited axle torque request in the vehicle.

[0011] In addition to one or more of the features described herein, the processor is further configured to determine the limited axle torque request as a minimum value of the axle torque request and the upper axle torque limit.

[0012] In addition to one or more of the features described herein, the processor is further configured, when the direction of power flow is in a forward gear, to determine the upper axle torque limit to a first value when the road grade is within a zero grade range having an upper grade threshold, a second value greater than the first value when the road grade is a positive value greater than the upper grade threshold, or the first value when the road grade is negative.

[0013] In addition to one or more of the features described herein, the processor is further configured, when the direction of power flow is in a reverse gear, to determine the upper axle torque limit to a first value when the road grade is within a zero grade range with a lower grade threshold, the first value when the road grade is positive, or a second value greater than the first value when the road grade is negative and less than the lower grade threshold.

[0014] In addition to one or more of the features described here, the upper axle torque limit increases with increasing road gradient when the vehicle is traveling uphill.

[0015] In addition to one or more of the features described herein, the processor is further configured to select a default road grade value when a road grade measurement is invalid and / or a power flow direction is invalid.

[0016] In addition to one or more of the features described here, the road inclination sensor is an acceleration sensor.

[0017] In yet another exemplary embodiment, a vehicle is disclosed. The vehicle includes a road gradient sensor for measuring a road gradient of a road section traveled by the vehicle, a speedometer for measuring the vehicle speed, a power flow direction sensor for determining a direction of the vehicle's power flow, a pedal position sensor for measuring the pedal position, and a processor.The processor is configured to determine an upper axle torque limit for an engine of the vehicle based on road grade, vehicle speed, and direction of power flow, determine an axle torque request based on vehicle speed and pedal position, determine a limited axle torque request from the axle torque request and the upper axle torque limit, and control the vehicle by implementing the limited axle torque request in the vehicle.

[0018] In addition to one or more of the features described herein, the processor is further configured to determine the limited axle torque request as a minimum value of the axle torque request and the upper axle torque limit.

[0019] In addition to one or more of the features described herein, the processor is further configured, when the direction of power flow is in a forward gear, to determine the upper axle torque limit to a first value when the road grade is within a zero grade range having an upper grade threshold, a second value greater than the first value when the road grade is a positive value greater than the upper grade threshold, or the first value when the road grade is negative.

[0020] In addition to one or more of the features described herein, the processor is further configured, when the direction of power flow is in a reverse gear, to determine the upper axle torque limit to a first value when the road grade is within a zero grade range with a lower grade threshold, the first value when the road grade is positive, or a second value greater than the first value when the road grade is negative and less than the lower grade threshold.

[0021] In addition to one or more of the features described here, the upper axle torque limit increases with increasing road gradient when the vehicle is traveling uphill.

[0022] In addition to one or more of the features described herein, the processor is further configured to select a default road grade value when a road grade measurement is invalid and / or a power flow direction is invalid.

[0023] The above-described features and advantages and other features and advantages of the disclosure will become apparent from the following detailed description when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Further features, advantages and details appear only as examples in the following detailed description, which refers to the drawings; they show: Fig. 1 an embodiment of a vehicle in an exemplary embodiment; Fig. 2 shows a relationship between the upper axle torque limit and the road gradient for a vehicle in forward gear in an exemplary embodiment; Fig. 3 three road gradients traversed by an electric vehicle with its drive unit in forward gear; Fig. 4 shows a relationship between the axle torque limit and the road gradient for a vehicle in forward gear in an exemplary embodiment; Fig. 5 the three road gradients travelled by the electric vehicle with its drive unit in reverse gear; Fig. 6 is a schematic diagram of a process flow for implementing an axle torque limit based on road gradient in an exemplary embodiment; and Fig. 7 a flowchart of a method for implementing a limited axle torque request in the electric vehicle. DETAILED DESCRIPTION

[0025] The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application, or uses. It should be understood that throughout the drawings, corresponding reference numerals designate similar or corresponding portions and features. As used herein, the term module refers to processing circuitry that may include an application-specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) with memory executing one or more software or firmware programs, a combinational logic circuit, and / or other suitable components that provide the described functionality.

[0026] According to an exemplary embodiment, Fig. 1 illustrates an embodiment of a vehicle 10 including a vehicle body 12 that at least partially defines a passenger compartment 14. The vehicle body 12 also supports various vehicle subsystems, including a propulsion system 16 and other subsystems to support functions of the propulsion system 16, and other vehicle components such as a braking subsystem, a suspension system, a steering subsystem, and others.

[0027] The vehicle 10 may be an electric vehicle (EV), an internal combustion engine vehicle, a hybrid vehicle, or another type of vehicle. For illustrative purposes, the vehicle 10 is an electric vehicle that includes multiple motors and / or drive systems. Any number of drive units may be included, such as one or more drive units for applying torque to front wheels (not shown) and / or rear wheels (not shown). The drive units are controllable to operate the vehicle 10 in various operating modes, such as a normal mode, a high-performance mode (in which additional torque is applied), all-wheel drive ("AWD"), front-wheel drive ("FWD"), rear-wheel drive ("RWD"), and others.

[0028] For example, the propulsion system 16 is a multiple drive system that includes a front drive unit 20 for driving front wheels and rear drive units for driving rear wheels. The front drive unit 20 includes a front electric motor 22 and a front inverter 24 (e.g., a front power inverter module or FPIM), as well as other components such as a cooling system. A left rear drive unit 30L includes a left rear electric motor 32L and a left rear inverter 34L. A right rear drive unit 30R includes a right rear electric motor 32R and a right rear inverter 34R. The front inverter 24, the left rear inverter 34L and the right rear inverter 34R (e.g., power inverter units or PIMs) each convert direct current (DC) power from a high-voltage (HV) battery system 40 to multi-phase alternating current (AC) power (e.g.,Two-phase AC power, three-phase AC power, six-phase AC power, etc.) (multi-phase AC power) to drive the front electric motor 22, the left rear electric motor 32L, and the right rear electric motor 32R.

[0029] As in Fig. As shown in Figure 1, the drive systems comprise separate electric motors. However, embodiments are not so limited. For example, instead of separate motors, multiple drives may be provided by a single machine having multiple sets of windings that are physically independent.

[0030] As in Fig. 1, the drive systems are configured such that the front electric motor 22 drives the front wheels (not shown) and the left rear electric motor 32L and right rear electric motor 32R drive the rear wheels (not shown). However, embodiments are not so limited, as any number of drive systems and / or motors may be present at various locations (e.g., one motor driving each wheel, partner motors per axle, etc.). Additionally, embodiments are not limited to a dual drive system, as embodiments may be used with a vehicle having any number of motors and / or power inverters.

[0031] In the propulsion system 16, the front-wheel drive unit 20, the left rear-wheel drive unit 30L, and a right rear-wheel drive unit 30R are electrically connected to a battery system 40. The battery system 40 may also be electrically connected to other electrical components (also referred to as "electrical loads") such as vehicle electronics (e.g., via an auxiliary power module or APM 42), heating devices, cooling systems, and others. The battery system 40 may be configured as a rechargeable energy storage system (RESS).

[0032] In one embodiment, battery system 40 includes multiple separate battery assemblies, each battery assembly capable of being independently charged and used to independently supply power to a propulsion system or systems. For example, battery system 40 includes a first battery assembly, such as a first battery pack 44 connected to front inverter 24, and a second battery pack 46. First battery pack 44 includes multiple battery modules 48, and second battery pack 46 includes multiple battery modules 50. Each battery module 48, 50 includes a number of individual cells (not shown). In various embodiments, one or more of the battery packs may include a MODACS (multi-output dynamically adjustable capacity) battery.

[0033] Each of the front electric motor 22 and the left rear electric motor 32L and the right rear electric motor 32R is a three-phase motor having three-phase motor windings. However, the embodiments described herein are not so limited. For example, the motors may be any multi-phase machines powered by multi-phase inverters, and the drive units may be implemented using a single machine having independent sets of windings.

[0034] The battery system 40 and / or the propulsion system 16 includes a switching system having various switching devices for controlling the operation of the first battery pack 44 and the second battery pack 46 and selectively connecting the first battery pack 44 and the second battery pack 46 to the front drive unit 20, the left rear drive unit 30L, and the right rear drive unit 30R. The switching devices are also operable to selectively connect the first battery pack 44 and the second battery pack 46 to a charging system. The charging system can be used to charge the first battery pack 44 and the second battery pack 46 and / or to supply power from the first battery pack 44 and / or the second battery pack 46 to charge another energy storage system (e.g., vehicle-to-vehicle (V2V) and / or vehicle-to-everything (V2X) charging). The charging system contains one or more charging modules.For example, a first on-board charging module (OBCM) 52 is electrically connected to a charging port 54 for charging to and from an AC system or device, such as a utility AC power supply. A second OBCM 53 may be included for DC charging (e.g., DC fast charging or DCFC).

[0035] In one embodiment, the switching system includes a first switching device 60 that selectively connects the first battery pack 44 to the front inverter 24, the left rear inverter 34L, and the right rear inverter 34R, and a second switching device 62 that selectively connects the second battery pack 46 to the front inverter 24, the left rear inverter 34L, and the right rear inverter 34R. The switching system also includes a third switching device 64 (also referred to as a "battery switching device") for selectively connecting the first battery pack 44 to the second battery pack 46 in series.

[0036] Any number of different controllers may be used to control functions of the battery system 40, the switching system, and the drive units. A controller includes any suitable processing device or processing unit and may utilize an existing controller such as a drive system controller, a RESS controller, and / or controllers within the drive system. For example, a controller 65 for ride control operations, as discussed herein, may be included.

[0037] The controller 65 may include processing circuitry, which may include an application-specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) with memory executing one or more software or firmware programs, a combinational logic circuit, and / or other suitable components that provide the described functionality.The controller 65 may include a non-transitory computer-readable medium storing instructions that, when processed by one or more processors of the controller 65, implement a method for determining an upper limit of axle torque that can be provided to an axle (or wheel) of the vehicle based on the road grade experienced by the vehicle, and for controlling operation of a powertrain to provide an axle torque that does not exceed the upper limit, in accordance with one or more of the embodiments described herein.

[0038] The vehicle 10 also includes a road grade sensor 70, a power flow direction sensor 72, a speedometer 74, and a pedal position sensor 76. The road grade sensor 70 can be used to determine or measure a road grade of a roadway section traveled by the vehicle. In various embodiments, the road grade sensor 70 is an accelerometer. The controller 65 monitors the road grade sensor 70 to determine validity of the road grade measurements. For example, a road grade measurement must be recorded for a sufficiently long period of time to be considered valid. The power flow direction sensor 72 detects a direction of power flow (i.e., forward, reverse) of the propulsion unit(s) of the vehicle 10. The speedometer 74 measures a speed of the vehicle 10 (vehicle speed).The pedal position sensor 76 detects a pedal position (ie, a position of an accelerator pedal).

[0039] The vehicle 10 also includes a computer system 55 that includes one or more processing devices 56 and a user interface 58. The computer system 55 can communicate with the charging system controller, e.g., to provide instructions in response to user input. The various processing devices, modules, and units can communicate with each other using a communication device or system, such as a controller area network (CAN) or a transmission control protocol (TCP) bus.

[0040] Fig. 2 shows, in an exemplary embodiment, a relationship 200 between the upper axle torque limit and road grade for a vehicle in forward gear. The road grade is plotted as a percentage (%) along the abscissa, and the upper axle torque limits (UL) are plotted along the ordinate. The upper axle torque limit is represented by curve 202. When the road grade is zero or near zero, the upper axle torque limit is at a first value (UL1), which is generally the smallest value for the limit. A zero grade range extends from a lower grade threshold A to an upper grade threshold B. For example, a zero grade range may range from about -5% to about +5%. For positive grades greater than the upper grade threshold, curve 202 slopes upward as the road grade increases.An example of a road gradient is shown at C along the abscissa, which refers to a second value for the upper axle torque limit. The second value is greater than the first value. For negative gradients less than the lower gradient threshold, curve 202 remains at the first value.

[0041] Fig. Figure 3 shows three road gradients traveled by an electric vehicle with its drive unit in forward gear. In a first forward gear scenario 302, the road gradient is zero or nearly zero (i.e., the vehicle is on horizontal or nearly horizontal terrain), and the torque limit is set to a first value (UL1) appropriate for such horizontal terrain. In a second forward gear scenario 304, the road gradient is a positive value (i.e., the vehicle is traveling uphill), and the torque limit is increased from the first value (UL1) to the second value (UL2). In a third forward gear scenario 306, the road gradient is negative (i.e., the vehicle is traveling downhill), and the torque limit is maintained at the first value (UL1).

[0042] Fig. 4 shows, in an exemplary embodiment, a relationship 400 between the axle torque limit and road gradient for a vehicle in forward gear. The road gradient is plotted as a percentage (%) along the abscissa, and the upper axle torque limits (UL) are plotted along the ordinate. The limit is represented by curve 402. When the road gradient is zero or near zero, the upper axle torque limit is at a first value (UL1), which is generally the smallest value for the limit. For positive gradients, curve 402 remains at the first value (UL1). For negative gradients, curve 402 rises to a second value (UL2). An example of a road gradient is plotted at D along the abscissa, which relates to a second value (UL2) for the upper axle torque limit. The second value (UL2) is greater than the first value (UL1).

[0043] Fig. Figure 5 shows the three road gradients traveled by an electric vehicle with its drive unit in reverse gear. In a first reverse gear scenario 502, the road gradient is zero or nearly zero (i.e., the vehicle is on horizontal or nearly horizontal terrain), and the upper axle torque limit is set to the first value (UL1). In a second reverse gear scenario 504, the road gradient is positive (i.e., the vehicle is traveling downhill), and the torque limit is maintained at the first value. In a third reverse gear scenario 506, the road gradient is negative (i.e., the vehicle is traveling uphill), and the torque limit is increased from the first value (UL1) to the second value (UL2).

[0044] Fig. 6 is a schematic diagram 600 of a process flow for implementing an axle torque limit based on road grade according to an exemplary embodiment. The process flow includes the operation of various modules, such as a torque request module 602, a torque limit module 604, and a minimization module 606, executed in the processor of controller 65.

[0045] The torque request module 602 receives a pedal position 608 (from the pedal position sensor 76) and a vehicle speed 610 (from the speedometer 74). The torque request module 602 determines an axle torque request 612 using a pedal map that includes a mathematical relationship between the pedal position 608, the vehicle speed 610, and the axle torque request.

[0046] The torque limit module 604 receives a road grade percentage 614 (from the road grade sensor 70), a road grade validity signal 616 (from the controller 65), a power flow direction 618 (from the power flow direction sensor 72), and the vehicle speed 610 (from the speedometer 74). The torque limit module 604 calculates an upper axle torque limit 620 value based on these parameters. The upper axle torque limit 620 and the axle torque request 612 are provided to the minimization module 606, which generates a limited axle torque request 622. The limited axle torque request 622 is a minimum value of the upper axle torque limit 620 and the axle torque request 612.

[0047] Fig.7 is a flowchart 700 of a method for implementing a limited axle torque request 622 in the electric vehicle. The method begins in box 702, where a road grade is measured. In box 704, the validity of the road grade measurement is checked. If the road grade measurement is invalid, the method continues to box 708. Otherwise (i.e., the road grade measurement is valid), the method continues to box 706. In box 706, a direction of power flow is retrieved and checked for validity. If the direction of power flow is invalid, the method continues to box 708. Otherwise (i.e., the direction of power flow is valid), the method continues to box 710. In box 708, a default value for the road grade is assigned as the value of an edited road grade. From box 708, the method continues to box 718, which is explained further below.

[0048] In field 710, the direction of power flow is determined. If the drive unit is in forward gear, the method continues with field 712. In field 712, a sign of the road grade is maintained. In other words, a grade multiplier is set to +1. Returning to field 710: If the drive unit is in reverse gear, the method continues with field 714. In field 714, a sign of the road grade is reversed. In other words, the grade multiplier is set to -1.

[0049] Field 718 receives the slope multiplier and the road grade measurement, with the slope multiplier being received from either field 712 or field 714. The road grade measurement is received from field 716. In field 718, a processed road grade is generated by multiplying the road grade measurement by the slope multiplier. The processed road grade is transmitted to field 718.

[0050] In field 718, an upper axle torque limit is determined based on the processed road grade (from field 716) and the vehicle speed 610. The upper axle torque limit is passed to field 720. In field 720, the upper axle torque limit (from field 718) and the axle torque request 612 are compared to determine a limited axle torque request 622. The limited axle torque request is then implemented in the electric vehicle. The method ends with field 722.

[0051] The terms "a" and "an" do not imply a limitation of number, but rather denote the presence of at least one of the referenced elements. The term "or" means "and / or" unless clearly indicated otherwise by context. A reference throughout the application text to "an aspect" means that a particular element (e.g., a feature, structure, step, or property) described in connection with the aspect is included in at least one aspect described herein and may or may not be present in further aspects. In addition, it is to be understood that the described elements in the various aspects may be combined in any suitable manner.

[0052] When an element, such as a layer, film, region, or substrate, is referred to as "on" another element, it may be directly adjacent to the other element or may also have intervening elements present. In contrast, when an element is referred to as "directly adjacent" to another element, no intervening elements are present.

[0053] Unless otherwise specified herein, all examination standards shall be the most recent standard in force as of the filing date of this application or, if priority is claimed, the filing date of the earliest priority application in which the examination standard appears.

[0054] Unless otherwise defined, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0055] While the above disclosure has been described with reference to exemplary embodiments, those skilled in the art will understand that various changes may be made and equivalents may be substituted for elements without departing from the scope thereof. Additionally, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from its essential scope. Therefore, it is intended that the present disclosure not be limited to the particular embodiments disclosed, but will include all embodiments falling within its scope. legend

[0056] In the drawings, N stands for No and Y for Yes, and R and F stand for the directions of power flow.

Claims

[1] A method of operating a vehicle comprising: Measuring a road gradient of a road section traveled by the vehicle using a road gradient sensor mounted on the vehicle; Determining an upper axle torque limit for an engine of the vehicle based on road grade, vehicle speed, and the direction of vehicle power flow; Determining an axle torque request based on vehicle speed and a pedal position; Determining a limited axle torque request from the axle torque request and the upper axle torque limit; and Control the vehicle by implementing the limited axle torque request in the vehicle. [2] The method of claim 1, wherein the limited axle torque request is a minimum value of the axle torque request and the upper axle torque limit. [3] The method of claim 1, further comprising, when the direction of power flow is in a forward gear, determining the upper axle torque limit to one of the following values: (i) a first value when the road grade is within a zero grade range having an upper grade threshold; (ii) a second value greater than the first value when the road grade is a positive value greater than the upper grade threshold; or (iii) the first value when the road grade is negative. [4] The method of claim 1, further comprising, when the direction of power flow is in a reverse gear, determining the upper axle torque limit to one of the following values: (i) a first value when the road grade is within a zero grade range with a lower grade threshold; (ii) the first value when the road grade is positive; or (iii) a second value greater than the first value when the road grade is negative and less than the lower grade threshold. [5] The method of claim 1, wherein the upper axle torque limit increases with increasing road gradient when the vehicle is traveling uphill. [6] System for operating a vehicle, comprising: a road inclination sensor for measuring a road inclination of a road section traveled by the vehicle; a speedometer for measuring the vehicle speed; a power flow direction sensor for determining a power flow direction of the vehicle; a pedal position sensor for measuring the pedal position; and a processor configured to: determine an upper axle torque limit for an engine of the vehicle based on road gradient, vehicle speed, and the direction of power flow; determine an axle torque request based on vehicle speed and pedal position; determine a limited axle torque request from the axle torque request and the upper axle torque limit; and to control the vehicle by implementing the requirement of limited axle torque in the vehicle. [7] The system of claim 6, wherein the processor is further configured to determine the limited axle torque request as a minimum value of the axle torque request and the upper axle torque limit. [8] The system of claim 6, wherein the processor is further configured, when the direction of power flow is in a forward gear, to determine the upper axle torque limit to one of the following values: (i) a first value when the road grade is within a zero grade range having an upper grade threshold; (ii) a second value greater than the first value when the road grade is a positive value greater than the upper grade threshold; or (iii) the first value when the road grade is negative. [9] The system of claim 6, wherein the processor is further configured, when the direction of power flow is in a reverse gear, to determine the upper axle torque limit to one of the following values: (i) a first value when the road grade is within a zero grade range with a lower grade threshold; (ii) the first value when the road grade is positive; or (iii) a second value greater than the first value when the road grade is negative and less than the lower grade threshold. [10] The system of claim 6, wherein the upper axle torque limit increases with increasing road grade when the vehicle is traveling uphill.

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