SE542263C2

SE542263C2 - A method and a system for controlling acceleration of a cab of a vehicle in z-direction during a gear shift

Info

Publication number: SE542263C2
Application number: SE1750959A
Authority: SE
Inventors: Marcus Engman; Oskar Lindahl; Viktor Dahlgren
Original assignee: Scania Cv Ab
Priority date: 2017-07-25
Filing date: 2017-07-25
Publication date: 2020-03-31
Also published as: SE1750959A1; DE102018005655A1

Abstract

The invention relates to a method of controlling acceleration (a) of a cab (2) of a vehicle (1) in z-direction, which acceleration (a) in z-direction emanates from the output torque (T) of a propulsion source (4) of the vehicle (1); the propulsion source (4) is provided with an output shaft (22), which is connected to at least one driving wheel of the vehicle (1). The method comprises the step of: a) regulating the output torque(T) of the propulsion source (4) in response to a difference (e) between a reference acceleration (a) in z-direction and a measured acceleration (a) in z-direction for reducing the acceleration (a) of the cab (2) in z-direction. The invention also relates to a system (7), a computer program, a computer-readable medium and a vehicle (1).

Description

A METHOD AND A SYSTEM FOR CONTROLLING ACCELERATION OF A CAB OF A VEHICLE IN Z-DIRECTION DURING A GEAR SHIFT TECHNICAL FIELD The invention relates to a method and a system for controlling acceleration of a cab of a vehicle in z-direction according to the appended claims. The invention also relates to a computer program a computer-readable medium and a vehicle according to the appended claims.

BACKGROUND AND PRIOR ART Vehicle driveability, sense of control and comfort for the driver are important issues in the development of modern vehicles such as heavy vehicles, e.g. trucks or busses. Therefore, it may be important that the vehicle responds the driver’s requests and desires. In addition to altering hardware, the software for controlling the vehicle may be developed and improved for improving the driveability of the vehicle.

Gear shifting may be one of the areas where software for controlling the driveability of the vehicle might be used. A common way of shifting gears in a vehicle transmission is to control the transmitted torque from the engine to the clutch down to zero and thereafter shifting the gearbox into a neutral gear. The engine speed may thereafter be controlled for synchronization of the gears to be engaged. When the new gear is engaged the torque may be increased to a level that is demanded by the driver.

A powertrain of a vehicle may be defined as a group of components that generate power requested by the driver and transfer the power to the driving wheels of the vehicle and further to the road. Due to different characteristics and torsional effects in the powertrain, oscillations might occur when power and torque in the powertrain are changed.

The engine and transmission may be controlled during a gear shifting in order to control the behaviour of the powertrain. The behaviour of the powertrain may influence the vehicle driveability, sense of control and comfort for the driver.

The document US2013/0297109A1 discloses a vehicle having an electrically powered traction motor and a control system for controlling the vehicle. The traction motor may be selectively coupled to vehicle traction wheels by a clutch disposed there between. Altering the torque, or clutch pressure in one embodiment, based upon a difference between a rotational speed of a powertrain component and a filtered rotational speed of the powertrain component may dampen powertrain oscillations perceived by an occupant of the vehicle.

SUMMARY OF THE INVENTION The oscillations that may occur when power and torque in the powertrain are changed may be transferred to the cab of the vehicle and thus influence the vehicle driveability, sense of control and comfort for the driver. Even though the oscillations in the powertrain components are reduced, the cab of the vehicle may oscillate when changing torque during gear shifting due to change of the propulsion force of the vehide. The oscillations induced in the vehicle and thus in the cab may have different directions. The vertical direction in relation the driving direction of the vehicle may be defined as the z-direction. The driving direction of the vehicle may be defined as the x-direction. When changing torque during gear shifting the changing of propulsion force of the vehicle results in a torque about the driving wheels and driving shafts. Oscillations are induced in the z-direction of the cab of the vehicle when the torque about the driving wheels and driving shafts changes. These oscillations in the z-direction may be uncomfortable for the driver and passengers in the cab.

There is a need to further develop a method and a system that reduces discomfort in the cab due to movements induced by changing the propulsion force from the powertrain. There is also a need to further develop a method and a system in which the gear shift in a vehicle reduces cab movements from a comfort and driveability perspective. There is also a need to further develop a method and a system in which the gear shift in a vehicle reduces cab movements from a perspective of wear of components used in the suspension system of the cab.

The object of the invention is therefore to develop a method and a system that reduces discomfort in the cab due to movements induced by changing the propulsion force from the powertrain. Another object of the invention is to develop a method and a system in which the gear shift in a vehicle reduces cab movements from a comfort and driveability perspective. A further object of the invention is to develop a method and a system in which the gear shift in a vehicle reduces cab movements from a perspective of wear of components used in the suspension system of the cab.

The herein mentioned objects may be achieved by the above-mentioned method and system for controlling acceleration of a cab of a vehicle in z-direction according to the appended claims.

According to the invention a method of controlling acceleration of a cab of a vehicle in z-direction during a gear shift is provided, which acceleration in z-direction emanates from the output torque of a propulsion source of the vehicle. The propulsion source is provided with an output shaft, which is connected to at least one driving wheel of the vehicle. The method comprises the step of: a) regulating the output torque of the propulsion source in response to a difference between a reference acceleration in z-direction and a measured acceleration in z-direction for reducing the acceleration of the cab in z-direction.

The method may control the gear shift with respect to the comfort in the cab instead of the internal states of the powertrain. The comfort is improved by minimizing the accelerations in z-direction during the gear shift. The movements will be controlled by the propulsion source. Using the method to reduce the oscillations may not require any extra actuators with adapted control systems. Sustainability of dampers and springs may be improved if the cab movements are controlled and/or suppressed. The output torque of the propulsion source may be controlled so that the acceleration in the z-direction follows a reference acceleration set to a value considered comfortable. The propulsion source may be an internal combustion engine and/or an electrical machine.

According to a further aspect of the invention the method comprises the further step of: b) before step a): setting the reference acceleration in z-direction to a value considered acceptable for acceleration of the cab in z-direction.

The reference acceleration in z-direction may be set to a value that is considered acceptable and comfortable with experience from comfort investigations. Comfort experience may include a subjective element. Eliminating all vibrations in a vehicle may be the best comfort. However, different investigations may conclude that vibrations in the z-direction in the region of 4 and 8 Hz and vibrations in the x-direction in the region of 1 and 2 Hz may be most uncomfortable for the human body. Thus, vibrations in the z-direction in the region of 4 Hz and above may be of most interest to reduce.

According to a further aspect of the invention the method comprises the further step of: c) calculating a torque derivative based on the difference between the reference acceleration in z-direction and the measured acceleration in z-direction to achieve a torque derivative limit.

A torque derivative limit may be used to apply an output torque to deliver a desired acceleration in the z-direction of the cab. The acceleration in the z-direction of the front of a vehicle chassis frame and the acceleration in the z-direction of the cab are closely connected. Dynamics in z-direction between the front of the chassis frame and the cab may be compensated for. An algorithm may be used in a control arrangement for controlling the output torque derivative for optimal comfort. The offramp and onramp of the torque before and after shifting gears may be designed in different ways.

According to a further aspect of the invention the method comprises the further step of: d) increasing the torque derivative limit and the output torque if the difference between the reference acceleration in z-direction and the measured acceleration in zdirection is negative.

Before shifting of gears the torque may be reduced to zero. The decreased torque may represent a graphic offramp. The reference acceleration in z-direction is set to a value that is considered comfortable with experience from comfort investigations. The difference between the reference acceleration in z-direction and the measured acceleration in z-direction may be calculated by iteration of a control arrangement. If the difference is negative it means that a larger output torque may be applied to the drive wheels and the saturation limits defined by the torque derivative limit may be increased. Tuning parameters of a control arrangement for an offramp situation may be the reference acceleration in z-direction and a constant value added to the saturation limits in case the difference may be negative.

According to a further aspect of the invention the method comprises the further step of: d) keeping the torque derivative limit steady if the difference between the reference acceleration in z-direction and the measured acceleration in z-direction is positive.

If the difference between the reference acceleration in z-direction and the measured acceleration in z-direction is positive, it means that the acceleration in z-direction has reached the reference acceleration. Then the saturation represented by the torque derivative limit may be kept at the same level until difference between the reference acceleration in z-direction and the measured acceleration signal in z-direction is negative again. The tuning parameters of the offramp control arrangement are the reference acceleration in z-direction and a constant value added to the saturation limits in case the difference may be positive.

According to a further aspect of the invention the method comprises the further step of: d) decreasing the torque derivative limit if the difference between the reference acceleration in z-direction and the measured acceleration in z-direction is positive.

If the difference between the reference acceleration in z-direction and the measured acceleration in z-direction is positive, it means that the acceleration in z-direction has reached the reference acceleration. Then the saturation represented by the torque derivative limit may be decreased so that the difference between the reference acceleration in z-direction and the measured acceleration in z-direction may be zero or negative. The tuning parameters of the offramp control arrangement are the reference acceleration in z-direction and a constant value added to the saturation limits in case the difference may be positive.

According to a further aspect of the invention the method comprises the further step of: d) increasing the torque derivative limit and the output torque if the difference between the reference acceleration in z-direction and the measured acceleration in zdirection is positive.

After shifting of gears a torque from the driver may be requested. The increased torque may represent a graphic onramp. The reference acceleration in z-direction is set to a value that is considered comfortable with experience from comfort investigations. The difference between the reference acceleration in z-direction and the measured acceleration in z-direction may be calculated by iteration of a control arrangement. If the difference is positive it means that a larger output torque can be applied to the drive wheels and the saturation limits defined by the torque derivative limit may be increased. Tuning parameters of a control arrangement for an onramp situation may be the reference acceleration in z-direction and a constant value added to the saturation limits in case the difference may be positive.

According to a further aspect of the invention the method comprises the further step of: d) keeping the torque derivative limit and the output torque steady if the difference between the reference acceleration in z-direction and the measured acceleration in zdirection may be negative.

If the difference between the reference acceleration in z-direction and the measured acceleration in z-direction is negative the saturation represented by the torque derivative limit is kept at the same level until difference between the reference acceleration in z-direction and the measured acceleration signal in z-direction may be positive again. Tuning parameters of a control arrangement for an onramp situation may be the reference acceleration in z-direction and a constant value added to the saturation limits in case the difference may be negative.

According to a further aspect of the invention the method comprises the further step of: d) decreasing the torque derivative limit and the output torque if the difference between the reference acceleration in z-direction and the measured acceleration in zdirection is negative.

If the difference between the reference acceleration in z-direction and the measured acceleration in z-direction is negative the saturation represented by the torque derivative limit may be decreased until a difference between the reference acceleration in z-direction and the measured acceleration signal in z-direction may be positive again. Tuning parameters of a control arrangement for an onramp situation may be the reference acceleration in z-direction and a constant value added to the saturation limits in case the difference may be negative.

According to the invention a system for controlling acceleration of a cab of a vehicle in z-direction is provided, comprising a control arrangement, the control arrangement comprising: means for regulating the output torque of the propulsion source in response to a difference between a reference acceleration in z-direction and a measured acceleration in z-direction to reduce the acceleration of the cab in z-direction.

The system may comprise a control arrangement, that may control the gear shift with respect to the comfort in the cab instead of the internal states of the powertrain. The comfort is improved by minimizing the accelerations in z-direction during the gear shift. The movements will be controlled by the propulsion source. Using the system to reduce the oscillations may not require any extra actuators or control systems. Sustainability of dampers and springs may be improved if the cab movements may be controlled and/or suppressed. The output torque of the propulsion source may be controlled so that the acceleration in the z-direction follows a reference acceleration set to a value considered comfortable. The propulsion source may be an internal combustion engine and/or an electrical machine.

According to a further aspect of the invention the control arrangement may further comprise: means for setting the reference acceleration in z-direction to a value considered acceptable for acceleration of the cab in z-direction.

According to a further aspect of the invention the control arrangement may further comprise: means for calculating a torque derivative based on the difference between the reference acceleration in z-direction and the measured acceleration in z-direction to achieve a torque derivative limit.

A torque derivative limit may be used to apply an output torque to deliver a desired acceleration in the z-direction of the cab. The acceleration in the z-direction of the front of a vehicle chassis frame and the acceleration in the z-direction of the cab are closely connected. Dynamics in z-direction between the front of the chassis frame and the cab may be compensated for. An algorithm may be used in a control arrangement for controlling the output torque derivative for optimal comfort. The offramp and onramp of the torque before and after shifting of gears may be designed in different ways.

Additional objectives, advantages and novel features of the invention will be apparent to one skilled in the art from the following details, and through exercising the invention. While the invention is described below, it should be apparent that the invention may be not limited to the specifically described details. One skilled in the art, having access to the teachings herein, will recognize additional applications, modifications and incorporations in other areas, which are within the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS Below is a description of, as examples, preferred embodiments with reference to the enclosed drawings, in which: Fig. 1 shows schematically a vehicle in a side view provided with a system for controlling acceleration of a cab of the vehicle in z-direction according to an embodiment, Fig. 2 shows schematically a powertrain in a view from above provided with a system for controlling acceleration of a cab of the vehicle in z-direction according to an embodiment, Fig. 3 shows a graph over the variation of output torque in time during gear shifting, Fig. 4 shows a block diagram of a control arrangement according to an embodiment, and Fig. 5 shows a flow chart for a method of controlling acceleration of a cab of the vehicle in z-direction according to an embodiment.

DETAILED DESCRIPTION OF THE DRAWINGS Fig. 1 shows schematically a vehicle 1 in a side view, which may be provided with a system 7 for controlling acceleration of a cab 2 of the vehicle 1 in z-direction according to an embodiment. The vehicle 1 may also be provided with a powertrain 3 comprising a propulsion source 4, a clutch 5, a gearbox 6, a propeller shaft 10 and drive wheels 8. The propulsion source 4 may be a combustion engine and/or an electrical machine which may be coupled to the gearbox 6 via the clutch 5. The gearbox 6 may be connected to the drive wheels 8 of the vehicle 1 via the propeller shaft 10. The vehicle 1 may also comprise front wheels 9. The gearbox 6 may comprise gears 12 that may be shifted in to different gear ratios. The vehicle 1 may be a heavy vehicle 1, e.g. a truck or a bus. The vehicle 1 may alternatively be a passenger car. The vehicle 1 may be manually operated, remotely operated or autonomously operated. The vehicle 1 may be rear-wheel driven, which means that the power from the propulsion source 4 is connected to the rear wheels of the vehicle 1. Thus, the rear wheels may be the drive wheels 8 of the vehicle 1.

The cab 2 and the wheels 8, 9 may be suspended by means of springs and dampers 14 on a chassis frame 16 of the vehicle 1. The suspension of the cab 2 may reduce oscillations that may occur when driving on a road and when power and torque in the powertrain 3 are changed.

Sensor means 18, 19 may be arranged on the chassis frame 16, the cab 2 and the wheels 8, 9 for data collection. The sensor means 18, 19 may be accelerometers 18 and position sensors 19. The position sensors 19 at the wheels 8, 9 measure the distance between centre axis 21, 23 of the wheels 8, 9 and the chassis frame 16. The position sensors 19 between the chassis frame 16 and the cab 2 measure the distance between the cab 2 and chassis frame 16. The accelerometers 18 and position sensors 19 measure the acceleration and position in z-direction. The vertical direction in relation the driving direction of the vehicle 1 may be defined as the z-direction. The driving direction of the vehicle 1 may be defined as the x-direction. When the vehicle 1 is positioned on a road, the x-direction coincides with the longitudinal direction of the vehicle 1. The z-direction is orthogonal to the x-direction and vertical in relation to the road.

The oscillations that may occur in the cab when driving on a road and when power and torque from the propulsion source 4 is changed may emanate from the torque induced about the centre axis 21 of the rear wheels 8. The chassis frame 16 may act similar to a lever arm and the torque induced about the centre axis 21 is transferred to the cab via the chassis frame 16. A change in the torque from the propulsion source 4 and thus from the torque induced about the centre axis 21 may induce accelerations and oscillations in the z-direction of the cab.

Fig. 2 shows schematically a powertrain 3 in a view from above provided with a system 7 of controlling acceleration of a cab 2 of the vehicle 1 in z-direction according to an embodiment. The propulsion source 4, which may be an internal combustion engine and/or an electrical machine, may be provided with a flywheel 20 arranged on an output shaft 22 of the propulsion source 4. The power and torque from the propulsion source 4 may be transferred to the drive wheels 8 through the clutch 5, the gearbox 6, the propeller shaft 10, a differential means 24 and drive shafts 26.

A control unit 28 may be arranged for controlling of the acceleration of a cab 2 of the vehicle 1 in z-direction. The control unit 28 may be connected to the propulsion source 4, the clutch 5, the gearbox 6 and the accelerometers 18 and position sensors 19. The control unit 28 may comprise a computer 29, or a link to a computer 29, comprising a computer program P with programme code for receiving the data containing the driving conditions of the vehicle 1 in order to calculate and control the acceleration of a cab 2 of the vehicle 1 in z-direction. The program code may be executed in the computer 29. The control unit 28 may further comprise stored data in a memory M, or a link to readable data, containing parameters for a reference acceleration az,ref(fig. 4) in z-direction that is considered acceptable for acceleration az(fig. 4) of the cab 2 in z-direction and for different vehicle operation modes to control the acceleration of a cab 2 of the vehicle 1 in z-direction. A computer program product may comprise a computer-readable medium and the computer program P, which computer program P may be contained in said computer-readable medium.

Fig. 3 shows a graph over the variation of output torque in time during gear shifting. When shifting gears in the gearbox 6 the transmitted output torque Toutput(fig. 4) from the propulsion source 4 to the clutch 5 is controlled down to zero and thereafter the gearbox 6 is shifted into a neutral gear. The decreased output torque Toutputmay represent a graphic offramp 30 in fig. 3. The speed from the propulsion source 4 may thereafter be controlled for synchronization of the gears 12 to be engaged. When the new gear is engaged the output torque Toutputfrom the propulsion source 4 may be increased as a request from the driver of the vehicle 1. The increased torque may represent a graphic onramp 32 in fig. 3.

Fig. 4 shows a block diagram of a control arrangement 34 according to an embodiment. The control arrangement 34 comprising means for regulating the output torque Toutputof the propulsion source 4 in response to a difference e between a reference acceleration az,refin z-direction and a measured acceleration az,measin z-direction to reduce the acceleration azof the cab 2 in z-direction. The control arrangement 34 of the system 7 may control the gear shift with respect to the comfort in the cab 2 instead of the internal states of the powertrain 3. The comfort is improved by minimizing the accelerations in z-direction during the gear shift. The movements will be controlled by the propulsion source 4. Using the system 7 to reduce the oscillations may not require any extra actuators with adapted control systems. Sustainability of dampers and springs 14 may be improved if the cab 2 movements may be controlled and/or suppressed. The output torque of the propulsion source 4 is controlled so that the acceleration in the z-direction follows a reference acceleration az,refset to a value considered comfortable. The measured acceleration az,measof the cab 2 in the z-direction may alternatively be a predicted acceleration which may be based on different measured variables.

The control arrangement 34 may further comprise means for setting the reference acceleration az,refin z-direction to a value considered acceptable for acceleration azof the cab 2 in z-direction. The reference acceleration az,refin z-direction may be set to a value that is considered comfortable with experience from comfort investigations. Comfort experience may however include a subjective element and eliminating all vibrations in a vehicle 1 may be the best comfort. However, different investigations may conclude that vibrations in the z-direction in the region of 4 and 8 Hz and vibrations in the x-direction in the region of 1 and 2 Hz may be most uncomfortable for the human body. Thus, vibrations in the z-direction in the region of 4 Hz and above may be of most interest to reduce.

The control arrangement 34 may further comprise means, such as a first controller 36 for calculating a torque derivative dT based on the difference e between the reference acceleration az,refin z-direction and the measured acceleration az,measin z-direction to achieve a torque derivative limit dTlim. The torque derivative limit dTlimmay be used to apply an output torque Toutputto deliver a desired acceleration in the z-direction of the cab 2. The acceleration in the z-direction of the front of the chassis frame 16 and the acceleration in the z-direction of the cab 2 are closely connected. Dynamics in z-direction between the front of the chassis frame 16 and the cab 2 may be compensated for. An algorithm may be used in the control arrangement 34 for controlling the output torque derivative for optimal comfort. The offramp 30 and onramp 32 of the torque before and after shifting of gears may be designed in different ways.

A reference torque may be a torque that is requested by the driver. The requested torque Treqshould be reached but without inducing too large accelerations in the cab 2 in the z-direction. The reference torque and thus the requested torque Treqshould be zero at the end of the offramp 30 before shifting gears. At the end of the onramp 32 the reference torque and thus the requested torque Treqmay be identical to the torque at the beginning of the offramp 30, but may alternatively differ from that torque due to changed conditions during shifting gears.

Based on the torque derivative limit dTlimthe output torque Toutputmay be calculated and controlled in a second and third controller 38, 40. The output torque Toutputis compared to the requested torque Treqand when the output torque Toutputhas reached the requested torque Treqthe control arrangement 34 is deactivated.

The control arrangement 34 controls the onramp 32 and the offramp 30 so that that the oscillations of the powertrain 3 may be suppressed. Therefore, the onramp 32 and offramp 30 are modified in the control arrangement 34 to improve the comfort. It may be the shape of the offramp 30 and onramp 32 when shifting gears that may be modified in order to improve the comfort for the driver and passengers in the cab 2 of the vehicle 1. The time for gear shifting may be crucial in some situations. In an upward slope it may be important to perform the gear shifting in a short period of time in order to keep up the velocity and propulsion of the vehicle 1 before and under the gear shifting. Therefore, the period of time in that the onramp 32 and offramp 30 are being performed may be limited.

The saturation limits in the control arrangement 34 may be used to apply an engine torque which delivers a desired acceleration in the z-direction in the cab 2. The acceleration in the z-direction in the cab 2 may be used as feedback. Dynamics in z-direction between the chassis frame 16 and cab 2 may be compensated for in the control arrangement 34. A settling time may be constant or may be dynamic. The reference torque may be the requested torque Treqfrom the driver of the vehicle 1. The offramp 30 and onramp 32 may be designed in different ways.

The algorithm for the offramp 30 may be defined as: Image available on "Original document" The algorithm for the onramp 32 may be defined as: Image available on "Original document" The acceleration in the z-direction may be sensitive to large, abrupt changes in engine torque. Therefore the acceleration in z-direction may be used as feedback in the control arrangement 34 to calculate the difference e between the measured acceleration az,measand the reference acceleration az,ref. The control arrangement 34 may be a part of the control unit 28.

Fig. 5 shows a flow chart for a method of controlling acceleration of a cab 2 of the vehicle 1 in z-direction according to an embodiment. The vehicle 1 may comprise the features described in the embodiments above.

The method may comprise the step of: a) regulating the output torque Toutputof the propulsion source 4 in response to a difference e between a reference acceleration az,refin z-direction and a measured acceleration az.meas in z-direction for reducing the acceleration azof the cab 2 in z-direction.

The method may control the gear shift with respect to the comfort in the cab 2 instead of the internal states of the powertrain 3. The comfort is improved by minimizing the accelerations in z-direction during the gear shift. The movements will be controlled by the propulsion source 4. Using the method to reduce the oscillations may not require any extra actuators with adapted control systems. Sustainability of dampers and springs 14 may be improved if the cab 2 movements are controlled and/or suppressed. The output torque of the propulsion source 4 may be controlled so that the acceleration in the z-direction follows a reference acceleration az,refset to a value considered comfortable. The measured acceleration az,measof the cab 2 in the z-direction may alternatively be a predicted acceleration which may be based on different measured variables.

The method may comprise the further step of: b) before step a): setting the reference acceleration az,refin z-direction to a value considered acceptable for acceleration azof the cab 2 in z-direction.

The reference acceleration az,refin z-direction may be set to a value that is considered acceptable and comfortable with experience from comfort investigations. Comfort experience may include a subjective element. Eliminating all vibrations in a vehicle 1 may be the best comfort. However, different investigations may conclude that vibrations in the z-direction in the region of 4 and 8 Hz and vibrations in the x-direction in the region of 1 and 2 Hz may be most uncomfortable for the human body. Thus, vibrations in the z-direction in the region of 4 Hz and above may be of most interest to reduce.

The method may comprise the further step of: c) calculating a torque derivative dT based on the difference e between the reference acceleration az,refin z-direction and the measured acceleration az,measin z-direction to achieve a torque derivative limit dTlim.

A torque derivative limit dTlimmay be used to apply an output torque to deliver a desired acceleration in the z-direction of the cab 2. The acceleration in the z-direction of the front of a chassis frame 16 and the acceleration in the z-direction of the cab 2 are closely connected. Dynamics in z-direction between the front of the chassis frame 16 and the cab 2 may be compensated for. An algorithm may be used in a control arrangement 34 for controlling the output torque derivative for optimal comfort. The offramp 30 and onramp 32 of the torque before and after shifting gears may be designed in different ways.

The method may comprise the further step of: d) increasing the torque derivative limit dTlimand the output torque Toutputif the difference e between the reference acceleration az,refin z-direction and the measured acceleration az.meas in z-direction is negative.

Before shifting of gears the torque may be reduced to zero. The decreased torque may represent a graphic offramp 30. The reference acceleration az,refin z-direction is set to a value that is considered comfortable with experience from comfort investigations. The difference e between the reference acceleration az,refin z-direction and the measured acceleration az,measin z-direction may be calculated by iteration of the control arrangement 34. If the difference is negative it means that a larger output torque may be applied to the drive wheels 8 and the saturation limits defined by the torque derivative limit may be increased. Tuning parameters of the control arrangement 34 for an offramp 30 situation may be the reference acceleration az,refin z-direction and a constant value added to the saturation limits in case the difference may be negative. The constant value may be a value adapted for the system 7 and may be positive or negative depending on if the output torque Toutputshould be increased or decreased.

The method may comprise the further step of: d) keeping the torque derivative limit dTlimsteady if the difference e between the reference acceleration az,refin z-direction and the measured acceleration az,measin z-direction is positive.

If the difference e between the reference acceleration az,refin z-direction and the measured acceleration az,measin z-direction is positive, it means that the acceleration in z-direction has reached the reference acceleration az,ref. Then the saturation represented by the torque derivative limit dTlimmay be kept at the same level until difference e between the reference acceleration az,refin z-direction and the measured acceleration az,meassignal in z-direction is negative again. The tuning parameters of the offramp control arrangement 34 are the reference acceleration az,refin z-direction and a constant value added to the saturation limits in case the difference may be positive. The constant value may be a value adapted for the system 7 and may be positive or negative depending on if the output torque Toutputshould be increased or decreased.

The method may comprise the further step of: d) decreasing the torque derivative limit dTlimif the difference e between the reference acceleration az,refin z-direction and the measured acceleration az,measin z-direction is positive.

If the difference e between the reference acceleration az,refin z-direction and the measured acceleration az,measin z-direction is positive, it means that the acceleration in z-direction has reached the reference acceleration az,ref. Then the saturation represented by the torque derivative limit dTlimmay be decreased so that the difference e between the reference acceleration az,refin z-direction and the measured acceleration az,measin z-direction may be zero or negative. The tuning parameters of the offramp control arrangement 34 are the reference acceleration az,refin z-direction and a constant value added to the saturation limits in case the difference may be positive. The constant value may be a value adapted for the system 7 and may be positive or negative depending on if the output torque Toutputshould be increased or decreased.

The method may comprise the further step of: d) increasing the torque derivative limit dTlimand the output torque Toutputif the difference e between the reference acceleration az,refin z-direction and the measured acceleration az,measin z-direction is positive.

After shifting of gears a torque from the driver may be requested. The increased torque may represent a graphic onramp 32. The reference acceleration az,refin z-direction is set to a value that is considered comfortable with experience from comfort investigations. The difference e between the reference acceleration az,refin z-direction and the measured acceleration az,measin z-direction may be calculated by iteration of the control arrangement 34. If the difference is positive it means that a larger output torque can be applied to the drive wheels 8 and the saturation limits defined by the torque derivative limit may be increased. Tuning parameters of an the control arrangement 34 for an onramp 32 situation may be the reference acceleration az,refin z-direction and a constant value added to the saturation limits in case the difference may be positive. The constant value may be a value adapted for the system 7 and may be positive or negative depending on if the output torque Toutputshould be increased or decreased.

The method may comprise the further step of: d) keeping the torque derivative limit dTlimand the output torque Toutputsteady if the difference e between the reference acceleration az,refin z-direction and the measured acceleration az,measin z-direction may be negative.

If the difference between the reference acceleration az,refin z-direction and the measured acceleration az,measin z-direction is negative the saturation represented by the torque derivative limit dTlimis kept at the same level until difference e between the reference acceleration az,refin z-direction and the measured acceleration az,measin zdirection may be positive again. Tuning parameters of the control arrangement 34 for an onramp 32 situation may be the reference acceleration az,refin z-direction and a constant value added to the saturation limits in case the difference may negative. The constant value may be a value adapted for the system 7 and may be positive or negative depending on if the output torque Toutputshould be increased or decreased.

According to a further aspect of the invention the method comprises the further step of: d) decreasing the torque derivative dTlimlimit and the output torque Toutputif the difference between the reference acceleration az,refin z-direction and the measured acceleration az.meas in z-direction is negative.

If the difference between the reference acceleration az,refin z-direction and the measured acceleration az,measin z-direction is negative the saturation represented by the torque derivative limit dTlimmay be decreased until a difference between the reference acceleration az,refin z-direction and the measured acceleration az,meassignal in z-direction may be positive again. Tuning parameters of a control arrangement 34 for an onramp 32 situation may be the reference acceleration az,refin z-direction and a constant value added to the saturation limits in case the difference may be negative. The constant value may be a value adapted for the system 7 and may be positive or negative depending on if the output torque Toutputshould be increased or decreased.

The computer program comprising program code that, when said program code is executed in the computer 29, causes said computer 29 to carry out the above-mentioned method. The computer program product comprising the computer-readable medium and the computer program, which computer program is contained in said computer-readable medium.

The foregoing description of the preferred embodiments has been furnished for illustrative and descriptive purposes. It is not intended to be exhaustive, or to limit the embodiments to the variants described. Many modifications and variations will obviously be apparent to one skilled in the art. The embodiments have been chosen and described in order to best explicate principles and practical applications, and to thereby enable one skilled in the art to understand the embodiments in terms of its various embodiments and with the various modifications that are applicable to its intended use. The components and features specified above may, within the framework of the embodiments, be combined between different embodiments specified.

Claims

1. A method of controlling acceleration (az) of a cab (2) of a vehicle (1) in z-direction during a gear shift, which acceleration (az) in z-direction emanates from the output torque (Toutput) of a propulsion source (4) of the vehicle (1); the propulsion source (4) is provided with an output shaft (22), which is connected to at least one driving wheel of the vehicle (1), the method comprises the step of: a) regulating the output torque (Toutput) of the propulsion source (4) in response to a difference (e) between a reference acceleration (az,ref) in z-direction and a measured acceleration (az,meas) in z-direction for reducing the acceleration (az) of the cab (2) in z-direction.

2. The method according to claim 1, comprising the further step of: b) before step a): setting the reference acceleration (az,ref) in z-direction to a value considered acceptable for acceleration (az) of the cab (2) in z-direction.

3. The method according to any of claims 1 and 2, comprising the further step of: c) calculating a torque derivative (dT) based on the difference (e) between the reference acceleration (az,ref) in z-direction and the measured acceleration (az,meas) in z-direction to achieve a torque derivative limit (dTlim).

4. The method according to claim 3, comprising the further step of: d) increasing the torque derivative limit (dTlim) and the output torque (Toutput) if the difference (e) between the reference acceleration (az,ref) in z-direction and the measured acceleration (az,meas) in z-direction is negative.

5. The method according to claim 3, comprising the further step of: d) keeping the torque derivative limit (dTlim) steady if the difference (e) between the reference acceleration (az,ref) in z-direction and the measured acceleration (az,meas) in z-direction is positive.

6. The method according to claim 3, comprising the further step of: d) decreasing the torque derivative limit (dTlim) if the difference (e) between the reference acceleration (az,ref) in z-direction and the measured acceleration (az,meas) in z-direction is positive.

7. The method according to claim 3, comprising the further step of: d) increasing the torque derivative limit (dTlim) and the output torque (Toutput) if the difference (e) between the reference acceleration (az,ref) in z-direction and the measured acceleration (az,meas) in z-direction is positive.

8. The method according to claim 3, comprising the further step of: d) keeping the torque derivative limit (dTlim) and the output torque (Toutput) steady if the difference (e) between the reference acceleration (az,ref) in z-direction and the measured acceleration (az,meas) in z-direction is negative.

9. The method according to claim 3, comprising the further step of: d) decreasing the torque derivative limit (dTlim) and the output torque (Toutput) if the difference (e) between the reference acceleration (az,ref) in z-direction and the measured acceleration (az,meas) in z-direction is negative.

10. A computer program, wherein said computer program comprises programme code for causing a control unit (28) or a computer (29) connected to the control unit (28) to perform the method according to any of the preceding claims.

11. A computer-readable medium comprising instructions, which when executed by a control unit (28) or a computer (29) connected to the control unit (28), cause the control unit (28) or the computer (29) to perform the method according to any one of claims 1 -9.

12. A system (7) for controlling acceleration (az) of a cab (2) of a vehicle (1) in zdirection during a gear shift, comprising a control arrangement (34), the control arrangement (34) comprising: means for regulating the output torque (Toutput) of the propulsion source (4) in response to a difference (e) between a reference acceleration (az,ref) in z-direction and a measured acceleration (az,meas) in z-direction to reduce the acceleration (az) of the cab (2) in z-direction.

13. The system (7) according to claim 12, the control arrangement (34) further comprising: means for setting the reference acceleration (az,ref) in z-direction to a value considered acceptable for acceleration (az) of the cab (2) in z-direction.

14. The system (7) according to any of claims 12 and 13, the control arrangement (34) further comprising: means for calculating a torque derivative (dT) based on the difference (e) between the reference acceleration (az,ref) in z-direction and the measured acceleration (az,meas) in z-direction to achieve a torque derivative limit (dTlim).

15. A vehicle (1), comprising a system (7) according to any of claims 12 - 14.