SE542776C2 - Control unit performing dynamic wheel slip target traction control - Google Patents

Abstract

The disclosure relates to a method (400) performed by a control unit (210) adapted to be comprised in a vehicle (110), the method comprising controlling (410) rotational speed (rod) of a drive unit (DU) coupled to at least one wheel of the vehicle (110) to a first rotational speed (ωd-i) using a target wheel slip value (WSTarget), obtaining (420) first traction force data, indicative of a first tractive force (FT1) of the vehicle (110) when the drive unit (DU) is operating at the first rotational speed (ωd-i), determining (430) an updated target wheel slip value ( WSτarget_updated ) using the first traction force data, controlling (440) the rotational speed (rod) of the drive unit (DU) of the vehicle (210) to a second rotational speed (rod2) using the updated target wheel slip value(WSτarget updated) .

Description

CONTROL UNIT PERFORMING DYNAMIC WHEEL SLIP TARGET TRACTION CONTROL Technical Field The present invention relates to control unit adapted to be comprised in a vehicle. The invention further relates to a corresponding method, computer program, computer program product, carrier and a vehicle comprising the control unit.

Background Modern vehicles often comprise a traction control system that mitigates the loss of road grip of a vehicle, mainly due to a difference in traction of the drive wheels. Difference in wheel slip may occur e.g. due to turning of a vehicle or varying road conditions for different wheels, typically due to that the road surface have or experience varying friction coefficients.

In one example, when a vehicle turns, its outer and inner wheels rotate at different speeds; this may conventionally be controlled by using a differential or an active differential, e.g. a controlled limited-slip differential. For example, if outward slip is sensed while turning, the active differential may deliver more/less power to the outer wheel in order to minimize the wheel slip. An active differential may be controlled using an assembly of sensors collaborating with a control unit or traction control unit.

In one example, when a vehicle travels over a road surface having varying road conditions, a left and a right drive wheel coupled to a drive unit may rotate at different speeds; this may conventionally be controlled by using a breaking unit, e.g. comprising a breaking control unit such as an anti-skid braking system, ABS, control unit. For example, an increased wheel slip of the left drive wheel is sensed in relation to the right drive wheel, the breaking control unit may deliver more power to the right wheel in order to minimize the wheel slip, typically by applying brake friction to the left drive wheel. The breaking unit may be controlled using an assembly of sensors collaborating with a control unit or traction control unit.

A problem with such conventional systems is that frequently too much or too little torque is delivered to the drive wheels, resulting in a reduced tractive force of the vehicle. This is mainly due to that the control of the drive wheels either limits torque delivered to the wheels for a fixed time or by assuming a fixed target wheel slip.

A further disadvantage with such conventional systems is that a friction coefficient of the road surface needs to be known or estimated.

Thus, there is a need for an improved control unit, method and vehicle.

Objects of the invention An objective of embodiments of the present invention is to provide a solution which mitigates or solves the drawbacks and problems of conventional solutions described above.

Summary of the invention The above and further objectives are achieved by the subject matter of the independent claims. Further advantageous implementation forms of the invention are defined by the dependent claims.

According to a first aspect of the invention, this objective is achieved by a method performed by a control unit adapted to be comprised in a vehicle, the method comprising controlling rotational speed of a drive unit coupled to at least one wheel of the vehicle to a first rotational speed using a target wheel slip value, obtaining first traction force data, indicative of a first tractive force of the vehicle when the drive unit is operating at the first rotational speed, determining an updated target wheel slip value using the first traction force data, controlling the rotational speed of the drive unit of the vehicle to a second rotational speed using the updated target wheel slip value.

At least one advantage of the invention according to the first aspect is that the target wheel slip value can be determined close to an optimal or ideal wheel slip value for the present road surface conditions. A further advantage is that the friction coefficient of the road surface is not required to control the vehicle, thus the target wheel slip value can be determined with low or reduced delay or processing complexity by alleviating the need to obtain or estimate the friction coefficient of the road surface.

According to a second aspect of the invention, this objective is achieved by a control unit configured to perform the method according to the first aspect.

According to a third aspect of the invention, this objective is achieved by a vehicle comprising the control unit according to the second aspect.

The advantages of the second and third aspect of the invention are the same as for the first aspect of the invention.

Further applications and advantages of embodiments of the invention will be apparent from the following detailed description.

Brief description of the drawings Fig. 1 illustrates a vehicle subjected to a tractive force resulting from wheels acting on a road surface according to one or more embodiments of the present invention.

Fig. 2 illustrates a prior art method of determining a fixed target wheel slip value according to one or more embodiments of the present invention.

Fig. 3 shows illustrates a method of determining a dynamic target wheel slip value according to one or more embodiments of the present invention.

Fig. 4 shows a vehicle according to one or more embodiments of the present invention.

Fig. 5 shows details of a vehicle according to one or more embodiments of the present invention.

Fig. 6 shows details of control unit according to one or more embodiments of the present invention.

Fig. 7 shows a flowchart of a method according to one or more embodiments of the present invention.

A more complete understanding of embodiments of the invention will be afforded to those skilled in the art, as well as a realization of additional advantages thereof, by a consideration of the following detailed description of one or more embodiments. It should be appreciated that like reference numerals are used to identify like elements illustrated in one or more of the figures.

Detailed description An “or” in this description and the corresponding claims is to be understood as a mathematical OR which covers ”and” and “or”, and is not to be understand as an XOR (exclusive OR). The indefinite article “a” in this disclosure and claims is not limited to “one” and can also be understood as “one or more”, i.e., plural.

Fig. 1 illustrates a vehicle 110 subjected to a tractive force FT resulting from wheels 120 acting on a road surface according to one or more embodiments of the present invention. The wheels 120 typically comprise one or more drive wheels rotating with a speed cod and one or more freely rotating/free-rolling or non-driven wheels rotating with a speed cor. The vehicle 110 further comprises a control unit 210 communicatively coupled to at least one sensor or traction sensor TS, e.g. selected from any one of an acceleration sensor, a rotational speed sensor (121-124), a positioning sensor such as a Global Navigation Satellite System (GNSS) sensor, a radar sensor or a lidar sensor. The control unit 210 may comprise a single unit or multiple communicatively coupled units, such as Electronic Control Units ECUs. The control unit 210 is typically configured to control the rotational speed cod of drive wheels of the vehicle based on a target wheel slip value or slip ratio. Further examples of sensors, traction sensors or positioning sensors are Global Positioning System (GPS), Globalnaya navigatsionnaya sputnikovaya sistema GLONASS, BeiDou Navigation Satellite System (BDS) and Galileo sensors.

A wheel slip value may be calculated according to any suitable definition, e.g. any one of: Image available on "Original document" Where ?d signifies the rotational speed or angular velocity of at least one drive wheel and cor signifies the rotational speed or angular velocity of at least one free-rolling wheel.

In an example where the vehicle has a right and a left drive wheel and a right and a left freerolling wheel, the wheel slip value may be calculated using an average of the left and right wheels: Image available on "Original document" Where ?dr signifies the rotational speed or angular velocity of the right drive wheel, ?dl signifies the rotational speed or angular velocity of the left drive wheel, ?rr signifies the rotational speed or angular velocity of the right free-rolling wheel, ?rl signifies the rotational speed or angular velocity of the left free-rolling wheel.

In yet an example, the wheel slip value may be calculated using the Society of Automotive Engineers definition SAE J670: Image available on "Original document" Where ?d signifies the rotational speed or angular velocity of a drive wheel of the vehicle 110, RadiuSfree-rolling signifies the effective radius of a corresponding free-rolling tire, typically on the same side of the vehicle, and v signifies the velocity of the vehicle in the direction of travel.

The vehicle 110 may comprise e.g. a mining vehicle, a truck, a bus or a car, or any similar vehicle or other means of conveyance suitable for travelling on a road. The vehicle 110 may be driver controlled and/or driverless autonomously controlled vehicles in different embodiments. The vehicle 110 may use a conventional internal combustion engine (ICE) propulsion system, an electric propulsion system or a combination thereof (hybrid vehicle).

Fig. 2 illustrates a prior art method of determining a fixed target wheel slip value according to one or more embodiments of the present invention. Fig. 2 illustrates a diagram having normalized friction coefficient in the range of [0-1] on the vertical axis and wheel slip value or slip ratio in the range of [0-1] on the horizontal axis. The diagram further shows a plurality of curves, typically obtained via measurements, providing a relation between normalized friction coefficient and wheel slip value or slip ratio. The curves are associated to a number of road conditions on asphalt ranging from icy asphalt to dry asphalt. For all curves, a maximum of friction may be identified, which gives the corresponding wheel slip value.

Some conventional systems for traction control attempts to utilize predetermined relations, such as the one illustrated in Fig. 2, to obtain a fixed target wheel slip value. This is typically performed by identifying the maxima of a curve described above. This further involves one way or another, to make an assumption or estimation of the road surface conditions, such as icy asphalt or dry asphalt to identify the corresponding curve.

At least one disadvantage of these conventional systems for traction control is that computational complexity is increased and processing time is delayed as an assumption, determination or estimation of the road surface conditions must be performed to obtain the target wheel slip value. Yet a disadvantage of these conventional systems for traction control is that deviation of the target wheel slip value from an optimal or ideal wheel slip value increases when the road surface conditions change rapidly or the road surface conditions varies greatly between wheels of the vehicle. Yet a disadvantage of these conventional systems for traction control is that measurements for all road surface conditions may not be available, further degrading the determination of the target wheel slip value.

The present disclosure overcomes or reduces these shortcomings or disadvantages of conventional systems for traction control by monitoring the tractive force FT resulting from wheels 120 acting on the road surface and dynamically adapting or determining the target wheel slip value using the tractive force FT.

Fig. 3 illustrates a method of determining a dynamic target wheel slip value according to one or more embodiments of the present invention. Fig. 3 shows a diagram with the dynamically determined target wheel slip value or updated target wheel slip value on the vertical axis and time elapsed on the horizontal axis.

The control unit 210 controls the rotational speed rod of a drive unit DU coupled to at least one wheel or drive wheel 120 of the vehicle 110 to a first rotational speed ?di using an initial target wheel slip value WSTarget at a first point in time. Traction force data is then obtained, indicative of a first tractive force Fn of the vehicle 110 when the drive unit DU is operating at the first rotational speed ?d1.

An updated target wheel slip value WSTarget updated for a second point in time, subsequent to the first point in time, is then determined using the first traction force data indicating the first tractive force FT1.

The rotational speed rod of the drive unit DU of the vehicle 210 is then controlled to a second rotational speed ?d2 using the updated target wheel slip value WSTarget_updated.

An updated target wheel slip value may be determined for each drive wheel of the vehicle 110.

This procedure may then be repeated continuously, until the vehicle is turned off or until the function is deactivated. The resulting series of updated target wheel slip values are illustrated in Fig. 3.

In other words, the tractive force FT resulting from wheels 120 acting on the road surface is monitored and the target wheel slip value is dynamically adapted or determined using the monitored tractive force FT. As can be seen in Fig. 3, the updated target wheel slip value WSiarget is reduced or lowered automatically when the drive wheel being controlled moves from a road surface having a relatively higher friction coefficient to a road surface having a relatively lower friction coefficient, e.g. from dry asphalt to icy asphalt.

The result of the determination of the updated target wheel slip value WSTarget_updated can be seen in Fig. 3. One way to determine the updated target wheel slip value WSTarget_updated comprises determining a wheel slip change value AWS, adding the wheel slip change value AWS to the initial or previously determined target wheel slip value WSTarget for the previous point in time to obtain a target wheel slip value WSTarget_updated for the present point in time.

The wheel slip change value AWS is determined to a positive value if the first tractive force Fit is equal to or greater than at least one historic value of tractive force indicated by the traction force data. Alternatively, the wheel slip change value AWS is determined to a negative value if the first tractive force FT1 is less than at least one historic value of tractive force indicated by the traction force data. In other words, the wheel slip value is increased until a point when it is determined that such an increase does not contribute to an increased traction force. The target wheel slip value is than backed off or reduced to increase the traction force of the vehicle.

The effect of this feature is that the target wheel slip value WSiarget updated can be determined close to an optimal or ideal wheel slip value for the present road surface conditions. The target wheel slip value WSTarget_updated can further be determined with low or reduced delay or processing complexity. This oscillating behavior around an optimal or ideal wheel slip value for the present road surface conditions can be seen as oscillations in the curve shown in Fig. 3.

In one embodiment, a filtered result of the tractive force is used to determine the updated target wheel slip value, typically by filtering first tractive force FT1 and historic values of the tractive force obtained at previous points in time. Examples of such filtering may be performed using low-pass, high-pass or averaging filters as would be understood by a person skilled in the art.

In one embodiment the magnitude the wheel slip change value AWS is determined to a relatively high value initially or when the road surface conditions change, e.g. indicated by a sudden change in tractive force FT or wheel spin of a drive wheel. The wheel slip change value AWS may then be determined with decreasing absolute value over time if the road surface conditions remain the same. In other words, the wheel slip change value AWS is initially determined to a nominal wheel slip change value and to a wheel slip change value AWS with decreasing absolute value over time as long as the road surface conditions remain the substantially the same.

Fig. 4 shows a vehicle 110 according to one or more embodiments of the present invention. As described in relation to Fig. 1, the vehicle 110 comprises a control unit 210 communicatively coupled to the drive unit, DU. The vehicle is further provided with wheels 120 acting on a road surface according to one or more embodiments of the present invention. The wheels 120 typically comprise one or more drive wheels W3, W4 coupled to the drive unit, DU, and rotating with corresponding speeds ?d2 and ?d4 and one or more freely rotating/free-rolling or non-driven wheels W1, W2, W5, W6 rotating with corresponding speeds ?r., ?r2, ?r5 , ?r6,The drive unit, DU, may be coupled to the drive wheels by coupling means in any suitable manner such that the rotational speed is transferred from the drive unit, DU, to the wheels, e.g. via a drive shaft, drive chain or drive belt.

In the example shown in Fig. 4, the vehicle is provided with two drive wheels W3 and W4 rotating with a speed or angular velocity of ?dW3 and ?dw4 respectively. The freely rotating/free-rolling or non-driven wheels W1, W2, W5, W6 are rotating with speeds ?rw1, ?rw2, ?rw5, ?rw6 respectively.

The control unit 210 may be configured to control driving power to one or more of the drive wheels W3-W4 of the vehicle causing them to rotate with a speed or angular velocity of ?dw 3 and ?dw4 respectively. The control unit 210 may comprise control logic and/or a processor, an optional memory. The drive unit DU may be configured to receive control signals from the control unit 210 and e.g. control one or more actuators based on the received control signals. The drive unit DU may further be configured to send status signals to the control unit 210 indicative of status of the drive unit DU, e.g. indicating a failure. The drive unit DU may comprise powertrain means, such as any means or arrangement suitable to delivering driving power and/or rotational speed to one or more of the drive wheels W3-W4 of the vehicle, e.g. the motor, engine and/or driving means, the transmission, the drive shafts, the differentials, and the final drive, e.g. acting on the drive wheels W3-W4 of the vehicle. The vehicle may further comprise one or more sensors (not shown in the figure) configured to receive and/or obtain and/or measure physical properties pertaining to the vehicle 120 and send one or more sensor signals comprising sensor data indicative of the physical properties of the vehicle 110 to the control unit 210, e.g. sensor data indicative of wheel speeds or angular velocity of wheels of the vehicle.

Fig. 5 shows details of a vehicle 110 according to one or more embodiments of the present invention. The drive unit DU may comprise powertrain means, wherein the powertrain means are selected from any one of a motor unit M, a clutch unit CL, a transmission unit TRM a differential unit DIFF and wheel brakes B. The vehicle may further be provided with wheel speed or angular velocity sensors 121-124 at each wheel W1-W4.

The motor unit M may further be provided with a motor control unit MCU configured to control the motor unit to deliver a particular power and/or rotational speed in response to control signals received from the control unit 210, e.g. Controller Area Network, CAN bus, signals. E.g. to control a throttle of the engine, a hydraulic retarder, an electric machine or an exhaust brake of the motor unit.

The clutch unit CL may further be provided with a clutch control unit CCU configured to control the clutch unit to engagement and disengagement of power transmission, typically from driving shaft to a driven shaft, in response to control signals received from the control unit 210, e.g. Controller Area Network, CAN bus, signals. E.g. to control a slippage between the driving shaft to the driven shaft.

The transmission unit TRM may further be provided with a transmission control unit TCU configured to control the transmission unit to provide speed and torque conversions of a rotational speed of an output shaft of the motor unit M to the rotational speed of the drive wheels W3-W4 in response to control signals received from the control unit 210, e.g. Controller Area Network, CAN bus, signals. E.g. controlling a gear selection of a gearbox.

The differential unit DIFF may further be provided with a differential control unit DCU configured to control drive power and/or the rotational speed of the drive wheels W3-W4 relative each other in response to control signals received from the control unit 210, e.g. Controller Area Network, CAN bus, signals. E.g. controlling rotational speed of the drive wheels W3-W4 individually and/or activate/deactivate limited-slip differential functionality and/or locking differential functionality.

The wheel brakes B may further be provided with a break control unit BCU configured to apply a friction force to the drive wheels W3-W4 and/or to the coupling means of the drive wheels W3-W4 in response to control signals received from the control unit 210, e.g. Controller Area Network, CAN bus, signals. E.g. controlling rotational speed of the drive wheels W3-W4 individually by applying a friction force.

The vehicle may further comprise wheel speed sensors configured to monitor the rotational or angular speed of each wheel W1-W4 respectively and send one or more sensor signals comprising sensor data indicative of wheel speeds or angular velocity of each wheel W1-W4 of the vehicle. The sensor data may then be used to calculate or determine wheel slip value or slip ratio.

The vehicle 110 may further comprise one or more environment sensors (Not shown in the figure). The one or more environment sensors may be configured to detect and/or register and/or capture first sensor data indicative of the environment of the vehicle. The one or more environment sensors may further be configured to send the first sensor data as a signal to the control unit 210. Examples of environment sensors may be any selection of radar sensor, lidar sensor, video camera, infrared camera, GPS with map, traffic information receiver or any other suitable environment sensor. In an example, the environment sensors 121-123 may include a radar detecting obstacles in front of the vehicle, such as pedestrians and/or other slow moving or stationary vehicles. In a further example, the environment sensors 121 -123 may include a camera detecting road markings in front of the vehicle, such as white lines outlining the road surface.

Fig. 6 shows a control unit 210 according to an embodiment of the present invention. The control unit 210 may be in the form of a selection of any of one or more Electronic Control Units, a server, an on-board computer, an digital information display, a stationary computing device, a laptop computer, a tablet computer, a handheld computer, a wrist-worn computer, a smart watch, a PDA, a Smartphone, a smart TV, a telephone, a media player, a game console, a vehicle mounted computer system or a navigation device. The control unit 210 may comprise a processor 112 communicatively coupled to a transceiver 104 for wired or wireless communication. Further, the control unit 210 may further comprise at least one optional antenna (not shown in figure). The antenna may be coupled to the transceiver 104 and is configured to transmit and/or emit and/or receive a wireless signals in a wireless communication system, e.g. send/receive control signals and/or status data to/from the drive unit DU, the one or more sensors 121-124 or any other control unit or sensor. In one example, the processor 112 may be any of a selection of processing circuitry and/or a central processing unit and/or processor modules and/or multiple processors configured to cooperate with each-other. Further, the control unit 210 may further comprise a memory 115. The memory 115 may contain instructions executable by the processor to perform the methods described herein. The processor 112 may be communicatively coupled to a selection of any of the transceiver 104, the one or more sensors 121-124 and the memory 115. The control unit 210 may be configured to receive the sensor data directly from the voltage sensor 120 or via a wired and/or wireless communications network 140.

The control unit 210 may further comprise a communications interface, e.g. the wireless transceiver 104 and/or a wired/wireless communications network adapter, which is configured to send and/or receive data values or parameters as a signal to or from the processing means 112 to or from other external nodes, e.g. a control information server 140. In an embodiment, the communications interface communicates directly between communication network nodes or via the communications network. In one or more embodiments the control unit 210 may further comprise an input device 117, configured to receive input or indications from a user and send a user-input signal indicative of the user input or indications to the processing means 112. In one or more embodiments the control unit 210 may further comprise a display 118 configured to receive a display signal indicative of rendered objects, such as text or graphical user input objects, from the processing means 112 and to display the received signal as objects, such as text or graphical user input objects. In one embodiment the display 118 is integrated with the user input device 117 and is configured to receive a display signal indicative of rendered objects, such as text or graphical user input objects, from the processing means 112 and to display the received signal as objects, such as text or graphical user input objects, and/or configured to receive input or indications from a user and send a user-input signal indicative of the user input or indications to the processing means 112. In embodiments, the processing means 112 is communicatively coupled to the memory 115 and/or the communications interface and/or the input device 117 and/or the display 118 and/or the one or more sensors 121-124. In embodiments, the communications interface and/or transceiver communicates using wired and/or wireless communication techniques. In embodiments, the one or more memory 115 may comprise a selection of a hard RAM, disk drive, a floppy disk drive, a magnetic tape drive, an optical disk drive, a CD or DVD drive (R or RW), or other removable or fixed media drive. In a further embodiment, the control unit 210 may further comprise and/or be coupled to one or more additional sensors configured to receive and/or obtain and/or measure physical properties pertaining to the vehicle 110 and send one or more sensor signals indicative of the physical properties to the processing means 112, e.g. second sensor data indicative of relative wheel speeds of the vehicle.

Fig. 7 shows a block diagram of a method according to one or more embodiments of the present invention. The method 700 may be performed by a control unit 210 adapted to be comprised in a vehicle 110, the method comprising: STEP 710: controlling rotational speed ?d of a drive unit DU coupled to at least one wheel of the vehicle 110 to a first rotational speed ?d1 using a target wheel slip value WSTarget.

Controlling the rotational speed ?d of a drive unit DU, e.g. of one or more output shafts thereof, is further described in relation to Fig. 5. In one example the throttling of the engine of the motor unit is increased when the tractive force Fn of the vehicle 110 is increasing, e.g. due to increasing friction coefficient of the road surface. In one further example the exhaust brake is activated when the tractive force Fn of the vehicle 110 is decreasing, e.g. due to decreasing friction coefficient of the road surface.

STEP 720: obtaining 720 first traction force data, indicative of a first tractive force FT1 of the vehicle 110 when the drive unit DU is operating at the first rotational speed ?d1.

In one embodiment, the first traction force data is obtained from a sensor selected from any of an acceleration sensor, a rotational speed sensor or wheel speed sensor 121-124, a Global Navigation Satellite System GNSS sensor, a radar sensor or a lidar sensor.

In one example, the first tractive force FT1 is calculated using an acceleration value of the vehicle and an estimated or predefined vehicle weight of the vehicle 110. In one example, the first tractive force FT1 is calculated using sensor data indicative of acceleration from an acceleration sensor and the predefined vehicle weight of the vehicle 110. In a further example, the first tractive force FT1 is calculated using sensor data from the rotational speed sensor or wheel speed sensor 121-124 and a predefined vehicle weight, e.g. by determining acceleration as a derivative value of obtained rotational speed or wheel speed over time and the predefined vehicle weight. In one example, the first tractive force FTi is calculated using sensor data from a Global Navigation Satellite System GNSS sensor as speed relative the road surface and the predefined vehicle weight of the vehicle 110. E.g. by determining acceleration of the vehicle 110 as speed change over time. In one example, the first tractive force FT1 is calculated using sensor data from a radar sensor or a lidar sensor, e.g. by calculating distance from the vehicle to a predefined reference point over time, and the predefined vehicle weight. . E.g. by determining acceleration of the vehicle 110 as distance change over time.

STEP 730: determining an updated target wheel slip value WSTarget_updated using the first traction force data.

In one embodiment, determining the updated target wheel slip value WSTarget_updated comprises increasing the updated target wheel slip value WSTarget_updated relative the target wheel slip value WSTarget if the first tractive force FT1 is equal to or greater than at least one first threshold or decreasing the updated target wheel slip value WSTarget_updated relative the target wheel slip value WSTarget if the first tractive force FT1 is the first threshold.

In one embodiment, determining the updated target wheel slip value WSTarget_updated comprises determining a wheel slip change value AWS and adding the wheel slip change value AWS to the target wheel slip value WSTarget, wherein the wheel slip change value AWS is determined to a positive value if the first tractive force FT1 is equal to or greater than at least one historic value of tractive force indicated by the traction force data, and wherein the wheel slip change value AWS is determined to a negative value if the first tractive force FT1 is less than at least one historic value of tractive force indicated by the traction force data.

In one embodiment, the first traction force data is obtained by filtering the first tractive force FTi and historic values of the tractive force.

In one embodiment, the wheel slip change value AWS is initially determined to a nominal wheel slip change value and to a wheel slip change value AWS with decreasing absolute value over time.

STEP 740: controlling the rotational speed ?d of the drive unit DU of the vehicle 210 to a second rotational speed ?d2 using the updated target wheel slip value WSTarget_updated.

In one embodiment, the step of controlling rotational speed ?d of the drive unit DU comprises controlling a selection of any of a motor unit M, a clutch unit CL, a transmission unit TRM, a differential unit DIFF or wheel brakes B of the drive unit DU of the vehicle 210.

Controlling the rotational speed ?d of the drive unit DU is further described in relation to STEP 710.

In one embodiment, a computer program is provided comprising computer-executable instructions for causing the control unit 210 when the computer-executable instructions are executed on a processing unit comprised in the control unit 210, to perform any of the methods described herein. Furthermore, any methods according to embodiments of the invention may be implemented in a computer program, having code means, which when run by processing means causes the processing means to execute the steps of the method. The computer program is included in a computer readable medium of a computer program product.

In one embodiment, a computer program product is provided comprising a computerreadable storage medium, the computer-readable storage medium having the computer program above embodied therein.

In one embodiment, a carrier containing the computer program above, wherein the carrier is one of an electronic signal, optical signal, radio signal, or computer readable storage medium.

In an embodiment, a computer program product comprising a memory and/or a computerreadable storage medium, the computer-readable storage medium having the computer program described above embodied therein. The memory and/or computer-readable storage medium referred to herein may comprise of essentially any memory, such as a ROM (Read-Only Memory), a PROM (Programmable Read-Only Memory), an EPROM (Erasable PROM), a Flash memory, an EEPROM (Electrically Erasable PROM), or a hard disk drive.

In embodiments, the communications network communicate using wired or wireless communication techniques that may include at least one of a Local Area Network (LAN), Metropolitan Area Network (MAN), Controller Area Network (CAN bus), Global System for Mobile Network (GSM), Enhanced Data GSM Environment (EDGE), Universal Mobile Telecommunications System, Long term evolution, High Speed Downlink Packet Access (HSDPA), Wideband Code Division Multiple Access (W-CDMA), Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Bluetooth®, Zigbee®, Wi-Fi, Voice over Internet Protocol (VoIP), LTE Advanced, IEEE802.16m, WirelessMAN-Advanced, Evolved High-Speed Packet Access (HSPA+), 3GPP Long Term Evolution (LTE), Mobile WiMAX (IEEE 802.16e), Ultra Mobile Broadband (UMB) (formerly Evolution-Data Optimized (EV-DO) Rev. C), Fast Low-latency Access with Seamless Handoff Orthogonal Frequency Division Multiplexing (Flash-OFDM), High Capacity Spatial Division Multiple Access (iBursl®) and Mobile Broadband Wireless Access (MBWA) (IEEE 802.20) systems, High Performance Radio Metropolitan Area Network (HIPERMAN), Beam-Division Multiple Access (BDMA), World Interoperability for Microwave Access (Wi-MAX) and ultrasonic communication, etc., but is not limited thereto.

Moreover, it is realized by the skilled person that the control unit 210 may comprise the necessary communication capabilities in the form of e.g., functions, means, units, elements, etc., for performing the present solution. Examples of other such means, units, elements and functions are: processors, memory, buffers, control logic, encoders, decoders, rate matchers, de-rate matchers, mapping units, multipliers, decision units, selecting units, switches, interleavers, de-interleavers, modulators, demodulators, inputs, outputs, antennas, amplifiers, receiver units, transmitter units, DSPs, MSDs, TCM encoder, TCM decoder, power supply units, power feeders, communication interfaces, communication protocols, etc. which are suitably arranged together for performing the present solution.

Especially, the processor and/or processing means of the present disclosure may comprise one or more instances of processing circuitry, processor modules and multiple processors configured to cooperate with each-other, Central Processing Unit (CPU), a processing unit, a processing circuit, a processor, an Application Specific Integrated Circuit (ASIC), a microprocessor, a Field-Programmable Gate Array (FPGA) or other processing logic that may interpret and execute instructions. The expression “processor” and/or “processing means” may thus represent a processing circuitry comprising a plurality of processing circuits, such as, e.g., any, some or all of the ones mentioned above. The processing means may further perform data processing functions for inputting, outputting, and processing of data comprising data buffering and device control functions, such as call processing control, user interface control, or the like.

Finally, it should be understood that the invention is not limited to the embodiments described above, but also relates to and incorporates all embodiments within the scope of the appended independent claims.

Claims (13)

1. A method (700) performed by a control unit (210) adapted to be comprised in a vehicle (110), the method comprising: controlling (710) rotational speed (rod) of a drive unit (DU) coupled to at least one wheel of the vehicle (110) to a first rotational speed ( ?d1 ) using a target wheel Slip Value (WSTarget), obtaining (720) first traction force data, indicative of a first tractive force (FT1) of the vehicle (110) when the drive unit (DU) is operating at the first rotational speed ( ?d1), determining (730) an updated target wheel slip value (WSTarget_updated) using the first traction force data, controlling (740) the rotational speed (rod) of the drive unit (DU) of the vehicle (210) to a second rotational speed (rod2) using the updated target wheel slip value (WSTarget_updated) , wherein determining the updated target wheel slip value (WSTarget_updated) comprises determining a wheel slip change value (AWS) and adding the wheel slip change value (AWS) to the target wheel slip value (WSTarget), wherein the wheel slip change value (AWS) is determined to a positive value if the first tractive force (FT1) is equal to or greater than at least one historic value of tractive force indicated by the traction force data, and, wherein the wheel slip change value (AWS) is determined to a negative value if the first tractive force (FT1) is less than at least one historic value of tractive force indicated by the traction force data.

2. The method according to claim 1, wherein the first traction force data is obtained by filtering the first tractive force (FT1) and historic values of the tractive force.

3. The method according to any of the preceding claims, wherein the wheel slip change value (AWS) is initially determined to a nominal wheel slip change value and to a wheel slip change value (AWS) with decreasing absolute value over time.

4. The method according to any of the preceding claims, wherein the step of controlling rotational speed (rod) of the drive unit (DU) comprises controlling the power output of a motor (M) comprised in the drive unit (DU).

5. The method according to claim 4, wherein the step of controlling rotational speed (rod) of the drive unit (DU) further comprises controlling one or more braking control units (BCU) units of the drive unit (DU).

6. The method according to any of claim 4-5, wherein the step of controlling rotational speed (rod) of the drive unit (DU) further comprises a controlling clutch control unit (CCU1) units of the drive unit (DU).

7. The method according to any of the preceding claims, wherein the first traction force data is obtained from a sensor selected from any of an acceleration sensor, a rotational speed sensor (121-124), a Global Navigation Satellite System (GNSS) sensor, a radar sensor or a lidar sensor.

8. A control unit (210) adapted to be comprised in a vehicle (110), the control unit (210) configured to perform the method according to any of claims 1-7.

9. A vehicle (110) comprising: drive unit (DU) coupled to at least one wheel (W3, W4) of the vehicle (110), the control unit (210) according to claim 8 communicatively coupled to the drive unit (DU).

10. The vehicle according to claim 9, further comprising an sensor communicatively coupled to the control unit (210), wherein the sensor is selected from any of an acceleration sensor, a rotational speed sensor (121-124), a Global Navigation Satellite System (GNSS) sensor, a radar sensor or a lidar sensor.

11. A computer program comprising computer-executable instructions for causing a control unit, when the computer-executable instructions are executed on a processing unit comprised in the control unit, to perform any of the method steps according claims 1-7.

12. A computer program product comprising a computer-readable storage medium, the computer-readable storage medium having the computer program according to claim 11.

13. A carrier containing the computer program according to claim 11, wherein the carrier is one of an electronic signal, optical signal, radio signal, or computer readable storage medium.