US-12617407-B2 - Method for controlling a heavy-duty vehicle

US12617407B2US 12617407 B2US12617407 B2US 12617407B2US-12617407-B2

Abstract

A method for controlling a powertrain system of a heavy-duty vehicle, the powertrain system having at least one differential arrangement for receiving torque from a propulsion unit of the powertrain system and delivering at least a part of the torque to a set of first and second wheels, the method being implemented by a control unit, the method comprising determining a split-friction condition indicative of a wheel slip difference between the first and second wheels, wherein one of the first and second wheels defines a high-friction side of the differential arrangement and the other one of the first and second wheels defines a low-friction side of the differential arrangement; determining a target wheel slip for the high-friction side; and in response to the determined split-friction condition; controlling a brake force on the low-friction side of the differential arrangement based on the target wheel slip on the high-friction side.

Inventors

Ramadan Salif
Viktor LÄGNERT

Assignees

VOLVO TRUCK CORPORATION

Dates

Publication Date: 20260505
Application Date: 20230105
Priority Date: 20220128

Claims (12)

1 . A method for controlling a powertrain system of a heavy-duty vehicle, the powertrain system having at least one differential arrangement for receiving torque from a propulsion unit of the powertrain system and delivering at least a part of the torque to a set of first and second wheels, the method being implemented by a control unit and comprising: determining a split-friction condition across a differential indicative of a wheel slip difference between the first and the second wheels by comparing a first wheel speed of the first wheel to a second wheel speed of the second wheel; identifying the first wheel as a high-friction side of the differential arrangement and the second wheel as a low-friction side of the differential arrangement; determining a target wheel slip for the high-friction side based on a relationship between a longitudinal tire force and a lateral tire force, the longitudinal tire force and the lateral tire force at least partially based on a road condition; and in response to the determined split-friction condition, controlling a brake force on the low-friction side of the differential arrangement to obtain the target wheel slip on the high-friction side.
2 . The method of claim 1 , wherein controlling the brake force on the low-friction side of the differential arrangement comprises controlling the revolution of an input axle of the differential arrangement based on the target wheel slip for the high-friction side.
3 . The method of claim 1 , wherein controlling the brake force on the low-friction side of the differential arrangement comprises controlling a brake pressure from the service brake.
4 . The method of claim 1 , wherein, if a wheel slip on the high-friction side exceeds the target wheel slip on the high-friction side, the method further comprises reducing a torque from the propulsion unit based on the target wheel slip on the high-friction side.
5 . The method of claim 1 , further comprising monitoring the individual wheel speeds of the first and the second wheels by using one or more wheel speeds sensors arranged and configured to determine corresponding wheel speeds of the first and the second wheels.
6 . The method of claim 1 , wherein the propulsion unit comprises any one of an electric machine, an internal combustion engine, and a fuel cell system.
7 . The method of claim 1 , further comprising: configuring a first wheel slip control module associated with the first driven wheel, and a second wheel slip control module associated with the second driven wheel, determining, by each wheel slip control module, an obtainable torque for the respective wheel based on a comparison between current wheel state and target wheel slip for the high-friction side, receiving a requested acceleration profile by the vehicle, determining a required torque to satisfy the requested acceleration profile, and requesting a torque from the propulsion unit corresponding to the smallest torque out of the obtainable torques for each driven wheel and the required torque.
8 . A control unit for performing the method of claim 1 .
9 . A vehicle comprising the control unit of claim 8 .
10 . A computer program comprising program code means for performing the method of claim 1 when the program is run on a computer or on processing circuitry of a control unit.
11 . The method of claim 1 , wherein the target wheel slip is set in response to required lateral force for steering or linear vehicle behavior, and longitudinal force for propulsion.
12 . The method of claim 1 , wherein the target wheel slip is set lower when lateral forces are required for steering or linear vehicle behavior, and higher when maximum longitudinal force is required for propulsion.

Description

RELATED APPLICATIONS The present application claims priority to European Patent Application No. 22153941.4, filed on Jan. 28, 2022, and entitled “METHOD FOR CONTROLLING A HEAVY-DUTY VEHICLE,” which is incorporated herein by reference in its entirety. TECHNICAL FIELD The present disclosure relates to methods and control units for controlling a powertrain system of a vehicle, such as a heavy-duty vehicle. In particular, the present disclosure relates to a method for controlling a powertrain system having a differential arrangement configured to be coupled to a propulsion unit. By way of example, the differential arrangement comprises an open differential. The present disclosure can be applied in heavy-duty vehicles, such as trucks and construction equipment. Although the present disclosure will be described mainly with respect to cargo transport vehicles such as semi-trailer vehicles and trucks, the disclosure is not restricted to this particular type of vehicle but may also be used in other types of vehicles such as electrically powered dolly units and passenger cars. BACKGROUND Heavy-duty vehicles, such as trucks and semi-trailer vehicles, are designed to carry heavy loads. Occasionally, such vehicles may be subject to so called split friction road conditions resulting in traction loss due to different friction between the wheels of the vehicle and the road. Such road conditions may occur e.g. in cold climates when one side of the lane is covered with snow or ice, and the other side is bare ground. In order to provide appropriate startability and tractive force in split friction conditions, the spinning wheel(s) of one or more wheel shafts of the vehicle may generally need to be braked in order to transfer torque to a high friction side of the wheel shafts. In many vehicle powertrain system for heavy-duty vehicles, this transfer of torque between the low friction side and the high friction side is provided by using a differential. A differential is a drive arrangement comprising three shafts. It has the property that the rotational speed of one shaft is the average of the speeds of the others, or at least a fixed multiple of that average. Another property is that during braking and propulsion, the wheel shafts will split the wheel longitudinal forces equally over the wheels. As such, the wheel force can be limited by the smallest force available from the left and right tyres. In trucks and other wheeled vehicles, the differential allows an outer drive wheel to rotate faster than an inner drive wheel during a turn. This may be beneficial as the vehicle turns, making the wheel that is traveling around the outside of the turning curve to roll farther than the other. The average of the rotational speed of the two driving wheels equals the input rotational speed of the drive shaft. An increase in the speed of one wheel is balanced by a decrease in the speed of the other. A differential normally transfers an equal amount of torque from the drive shaft to both wheels. However, if one wheel requires less power to turn than the other wheel, such as when one wheel is on dry pavement and the other on a muddy shoulder or on a spot of ice, it will take less torque to turn the wheel experiencing lower friction than to turn the wheel on the high friction roadway. By means of the mechanical function of the differential, such as an open differential, the wheel speeds between e.g. right and left sides can therefore spin at different speeds with respect to each other. Current traction control systems are usually configured to monitor the wheel speed signals to control the most spinning wheel or distribute brake torque to transfer according to the detected split friction condition. However, such systems may not always reflect the real conditions between the vehicle and the road. The problem may often be that the traction control function itself is configured to be suboptimized by calibration to work on unrealistic real conditions, such as asphalt/polished ice or basalt. In reality, the friction coefficients may be much closer to each other and the calibrated suboptimized function, causing the traction control function to provide unnecessary braking. Such excessive braking control may tear up the ground for the high friction wheel(s) causing even worse traction conditions for the vehicle. It would thus be desirable to provide a smoother traction control in view of the vehicle operation and the prevailing road surface conditions so as to provide an improved performance of the vehicle. SUMMARY It is an object of the present disclosure to provide an improved split friction handling for a vehicle so as to enhance the transfer of traction force. This object is achieved by a method according to claim 1. The objective is also achieved by the other independent claims. The dependent claims are directed to advantageous embodiments of the disclosure. According to a first aspect, there is provided a method for controlling a powertrain syst