Control of a semi-trailer having an electric drive machine

Abstract

A semi-trailer (110) is designed to be towed by a tractor (105) and comprises an electric drive machine (205) for providing a drive torque. A method (300) for controlling such an electric drive machine (205) comprises determining a tractive force acting on the semi-trailer (110), a travel speed of the semi-trailer (110), and an inclination of a base (140) of the semi-trailer (110). On the basis of the tractive force, the inclination and the travel speed, it is determined that the semi-trailer (110) is to be driven uphill, and the drive machine (205) is controlled in order to support the driving by means of a drive torque.

Description

[0001] Controlling a semi-trailer with an electric drive unit

[0002] The present invention relates to the control of a semi-trailer designed to be towed by a tractor. In particular, the invention relates to the control of a semi-trailer with an electric drive motor.

[0003] A semi-trailer is designed to be pulled by a tractor unit, so that the tractor unit and semi-trailer together form a semi-trailer combination. The semi-trailer may include an electric drive motor that acts on wheels on an axle of the semi-trailer. The electric drive motor can be controlled to assist the movement of the semi-trailer combination in predetermined driving situations.

[0004] It was proposed to control the torque provided by the electric drive motor as a function of the tractive force acting between the tractor and the trailer. A kingpin connecting the two vehicle parts can be equipped with a sensor to determine the tractive force.

[0005] Previously known controls for such an electric drive motor on a semi-trailer primarily support the tractor during cross-country travel and can, for example, provide support during uphill driving and control recuperation during downhill driving. One object underlying the present invention is to provide a technology for improved support of a semi-trailer using an electric drive motor. The invention solves this problem by means of the subject matter of the independent claims. Subordinate claims specify preferred embodiments.

[0006] A semi-trailer is designed to be towed by a tractor and includes an electric drive motor for providing drive torque. A method for controlling such an electric drive motor includes determining a tractive force acting on the semi-trailer, determining a travel speed of the semi-trailer, and determining an incline of a ground surface of the semi-trailer. Furthermore, the method includes determining, based on the tractive force, the incline, and the travel speed, that the semi-trailer is to be started uphill, and controlling the drive motor to assist the start with a drive torque.

[0007] According to the invention, the tractor unit can be assisted in starting the trailer on an uphill slope, i.e., on an incline. This makes it easier to break away or reach a certain speed at which the trailer can be safely controlled. For the tractor unit, the trailer can behave as if it had a lower mass or as if the incline were lower than it actually is. The assistance can be provided automatically, so that the tractor unit driver does not need to take any additional measures to start the trailer safely on the slope. Uncontrolled movement of the tractor unit, tractor unit, or trailer when starting off can be better prevented.

[0008] Starting can be determined when the determined travel speed is essentially zero. The travel speed can be determined based on the rotational speed of a wheel of the trailer, and the rotational speed can be zero or essentially zero.

[0009] A slope or gradient can be determined if the inclination of the ground in the approach direction exceeds a predetermined threshold. The inclination of the ground can be determined based on the trailer's orientation relative to the horizontal. For this purpose, an acceleration sensor can be provided, for example.

[0010] A vertical alignment of the trailer relative to the ground, i.e., a longitudinal or transverse inclination, generally has a negligible impact on starting on an incline. It should be noted that starting can occur forwards or backwards. A desired direction of travel can be determined based on the determined tractive force or on a reversing signal from the tractor unit. The driving speed can be determined using a speed sensor on one of the trailer's wheels. In alternative embodiments, a camera for scanning the ground or the surroundings of the trailer, an acceleration sensor, or a receiver for a satellite navigation system (GNSS) can be used to determine the driving speed of the trailer. Other ways of determining the speed of the trailer are also possible.

[0011] Preferably, it is determined that a drive wheel of the tractor is slipping based on a tractive force curve and a driving speed curve. Starting can only be assisted if slippage has been detected or if a specific slip exceeds a predetermined threshold.

[0012] In one embodiment, it is determined that the tractive force drops abruptly. In particular, the tractive force can drop at a predetermined minimum speed. The abrupt drop can indicate that a drive wheel of the tractor is suddenly spinning, so that the transferable propulsion force is suddenly reduced. It can be determined that the force immediately before the drop does not exceed a predetermined threshold. The threshold can be selected such that it can only be exceeded when starting on a surface with a medium or high coefficient of friction. The level of tractive force before the drop can thus indicate a surface with a low coefficient of friction.

[0013] Slipping typically occurs intermittently if the tractor unit has a traction control system. In a further embodiment, it can be determined that the tractive force oscillates at a frequency within a predetermined frequency range. The frequency range can include a typical or known operating frequency of a traction control system of the tractor unit. The frequency range can also include a natural frequency of the tractor unit or one of its components when a driver attempts to rock a stuck tractor-trailer out of position. In this way, the predetermined driving state can be determined automatically in an improved manner, without requiring an additional signal from the tractor unit. Furthermore, the driving state can also be determined if the tractor unit does not provide a corresponding signal.

[0014] Based on the driving speed and a VDC signal from the tractor unit, it can be determined that a drive wheel of the tractor unit is slipping. The VDC signal (“vehicle dynamics control active”) can indicate that an auxiliary function of the tractor unit for dynamic stabilization is active, in particular that a brake is being applied to influence the driving dynamics of the semi-trailer combination. The brake can be provided by the tractor unit or the semi-trailer. The VDC signal can be provided by various systems, such as an electronic stability program (ESP) or an anti-skid control (ASR). If the driving speed of the semi-trailer is below a predetermined threshold, which includes zero, the VDC signal can correspond to an ARS signal, which indicates that an anti-skid control system is active.

[0015] If available, an ASR signal from the tractor can be evaluated to determine the slippage of the tractor wheel. The ASR can specifically reduce the torque acting on a tractor's drive wheel if it detects that the drive wheel is slipping. The ASR signal can be used as an indicator that the tractor is having difficulty converting a desired drive torque into propulsion. In this case, the electric drive motor can be automatically activated to provide additional propulsion from the trailer.

[0016] The drive torque can be controlled depending on the trailer's mass. The mass can be determined, for example, based on the pressure in a hydraulic or pneumatic spring element of the trailer. The mass can also be determined using an observer or an adaptive filter, for example, based on a relationship between the drive torque and acceleration on the flat.

[0017] The drive torque can be controlled depending on the degree of incline or gradient being traveled. Assistance can only be controlled when the gradient exceeds a first predetermined threshold, for example, approximately 2°. Assistance can also be terminated or refused when the gradient exceeds a second predetermined threshold, for example, approximately 15%, which corresponds to a gradient of approximately 25°. In this case, safe starting may not always be possible, and there may be a risk of sideways skidding or sliding downhill. Terminated or refused assistance can be indicated by a signal, which can be provided, in particular, to a tractor driver.

[0018] Assistance can also be terminated if a braking request from the tractor unit is detected. The braking request can be for a service brake or a parking brake.

[0019] The start-off can be terminated if the driving speed exceeds a predetermined threshold. In one embodiment, this threshold can be selected such that it lies within a speed range achievable in a predetermined gear position of a drive system of the tractor. In another embodiment, the threshold can be set absolutely, for example, at approximately 3 km / h or approximately 6 km / h. It should be noted that the drive motor can also be activated by another assistance function beyond the threshold.

[0020] In a further embodiment, it is determined that the tractive force does not exceed a predetermined threshold during the start-up. If the tractive force exceeds the threshold, preferably if the driving speed simultaneously exceeds an assigned threshold, the start-up can be considered complete.

[0021] The drive torque can be controlled depending on the friction coefficient of a wheel driven by the drive motor on the ground. The friction coefficient between a drive wheel of the semitrailer and the ground can be determined by determining that the driven wheel is slipping. For this purpose, the wheel can be deliberately guided into slipping. To determine the friction coefficient, it is possible to determine the drive torque at which the wheel of the first axle begins to slip. The drive torque of the wheel can be well known within the context of the control of the electric drive motor. Particularly when field-oriented control is implemented, the torque provided by the electric drive motor can be selected as the control input.

[0022] The wheel can be driven in a slip-resistant manner, particularly in the manner of a dedicated traction control (ASR). The assistance can be controlled based on the coefficient of friction. The assistance is preferably provided in such a way that the slip at the wheel does not exceed a predetermined threshold. This threshold can be set to a low value, for example, approximately 15%, in particular approximately 10%.

[0023] 10% or approximately 5%, so that the wheel is held in static friction with the ground as much as possible. It can generally be assumed that a low coefficient of friction on a trailer wheel corresponds to a low coefficient of friction on a tractor wheel.

[0024] According to a further aspect of the present invention, a control device for a semi-trailer designed to be towed by a tractor is proposed. The semi-trailer comprises an electric drive motor for providing a drive torque. The control device comprises a first sensor for determining a tractive force acting on the semi-trailer, a second sensor for determining a driving speed of the semi-trailer, and a third sensor for determining an incline of a ground surface of the semi-trailer. The control device is designed to determine, on the basis of the determined tractive force, the determined driving speed, and the determined incline, that the semi-trailer is to be driven uphill and to control the drive motor to provide a drive torque to the wheel.

[0025] The control device may comprise an electronic processing device, which may in particular be embodied as a programmable microcomputer or microcontroller. The control device, in particular the processing device, may in particular be configured to partially or completely execute a method described herein. The method may be in the form of a computer program product with program code means. The computer program product may be stored on a computer-readable data carrier.

[0026] Features or advantages of the method can be transferred to the control device or vice versa.

[0027] According to yet another aspect of the invention, a semitrailer configured to be towed by a tractor comprises an electric drive motor for providing drive torque and a control device as described above. Such a semitrailer can also be called a semitrailer, semitrailer, or trailer. The semitrailer can be connected to a fifth wheel plate of the tractor by means of a kingpin. Part of the weight of the semitrailer then rests on the tractor. The semitrailer can be multi-axle and can, in particular, have two or three axles. A further proposed semitrailer combination comprises a semitrailer described herein and a tractor.

[0028] The invention will now be described in more detail with reference to the accompanying figures, in which

[0029] Fig. 1 a semi-trailer truck,

[0030] Fig. 2 a control device for a semi-trailer and

[0031] Fig. 3 shows a flow diagram of a method.

[0032] Fig. 1 shows a semitrailer truck 100 comprising a tractor unit 105 and a trailer 110. The semitrailer truck 100 and its components 105, 110 are, in particular, commercial vehicles. In the illustrated embodiment, the tractor unit 105 comprises a steered axle 115 and a drive axle 120. Other configurations are also possible. Typically, part of the weight of the trailer 110 rests on the tractor unit 105 in the area of ​​a drive axle 120.

[0033] The trailer 110 can be configured to transport any load. It comprises at least a first axle 125, which can be electrically driven. In the illustrated embodiment, a second axle 130 and a third axle 135 are additionally provided. The arrangement of the axles 125 to 135 can be different from that shown or described in other embodiments. Typically, the axles 125 to 135 are arranged at an end of the trailer 110 that is remote from the end bearing the load on the tractor 105.

[0034] Wheels, each attached to axles 125 to 135, rest or roll on a surface 140. The nature of the surface 140, for example, regarding its grip, evenness, or gradient, can influence the control with which the semitrailer 100 can be steered. In particular, when starting the semitrailer 100, unfavorable conditions may exist that make it difficult to control the semitrailer 100.

[0035] Fig. 2 shows a schematic representation of a control device 200 for a semi-trailer 110. The lower section shows the ground 140 and the wheels of the axles 125 to 135 of the semi-trailer 110. A direction of travel in Fig. 2 preferably runs to the left.

[0036] The trailer 110 includes an electric drive motor 205, which acts on a wheel on the first axle 125. An electrical energy source 210 may be provided to operate the drive motor 205. The energy source 210 is typically included in the trailer 110 and may, for example, comprise an electrochemical energy storage device, a generator, or a fuel cell. Conversion of electrical energy from the energy source 210 to the drive motor 205 typically includes a power converter, which is not shown in Fig. 2.

[0037] In one embodiment, the drive motor 205 can produce a propulsive force of approximately 10 to 15 kN if the wheel on the first axle 125 has good contact with the ground 140. It is possible for the drive motor 205 to be intended exclusively for operation at low driving speeds, for example, when starting or maneuvering. It is possible for the drive motor 205 to be switched off above a predetermined driving speed, for example, approximately 10 km / h. In another embodiment, the drive motor 205 can be controlled by means of various assistance functions, one of which can also allow propulsion at a higher driving speed.

[0038] A processing device 215 is configured to determine a driving situation in which the semi-trailer 110 is to be started on a slope and to control the drive motor 205 to assist the start. The drive motor 205 can be controlled by providing a power converter with appropriate control parameters, in particular a torque to be provided and / or a speed to be reached.

[0039] To determine the driving situation, the processing device 215 can be connected to a number of sensors. It should be noted that not all of the sensors or information sources shown in Fig. 2 need to be implemented in all embodiments of the invention.

[0040] A first sensor 220 is configured to determine a tensile force acting on the trailer 110. The tensile force can be applied, in particular, by the tractor 105. The first sensor 220 can be mounted, in particular, in the region of a kingpin that transmits tensile forces between the vehicles 105, 110. In one embodiment, strain gauges are used to determine a microscopic deflection of the kingpin under tensile load. A signal from the strain gauge can be appropriately amplified and further processed to determine a current tensile force based on a known bending behavior of the kingpin under the influence of tensile force.

[0041] A second sensor 225 is configured to determine a driving speed of the trailer 110. The second sensor 225 can comprise a speed sensor attached to a wheel of an axle 125-135 of the trailer 110 that has contact with the ground 140. Alternatively, a different second sensor 225 can be used that utilizes a different effect to determine the movement of the trailer 110. Multiple second sensors 225 can also be provided on different axles of the trailer 110. In one embodiment, the second sensor 225 is provided on a non-driven wheel. A third sensor 230 is configured to determine an inclination of the ground 140. For this purpose, an acceleration sensor can be used that determines the direction of the acceleration due to gravity with respect to the trailer 110.With respect to a known direction, when the trailer 110 is on a level surface 140, the inclination of the surface 140 with respect to the trailer 110 can be determined.

[0042] The inclination can be determined in magnitude and direction relative to a longitudinal axis of the trailer 110. The third sensor 230 can also comprise, for example, a type of pendulum or a gyroscope. Based on the determined inclination, a gradient can be determined that acts in the direction of the determined tractive force or in the direction of travel of the trailer 110.

[0043] In general, a gradient is defined here when the ground 140 rises in the direction in which the trailer 140 is pulled by the tractive force. The gradient may also run only partially in the direction of the tractive force and, in particular, form an acute angle with it, so that a resulting gradient may be smaller than an existing incline of the ground 140. This may be the case, for example, when the trailer combination 105, 110 starts up a slope diagonally uphill.

[0044] In general, it is assumed that the semi-trailer 110 always maintains the same orientation relative to the ground, regardless of its load. If this is not the case, the longitudinal orientation can be determined, for example, based on distance measurements to the ground 140 offset along a longitudinal axis of the semi-trailer 110. Such a distance can be determined, for example, using ultrasound, a camera, or a laser device. A distance can also be determined based on a spring travel prevailing on an axle 125-135. In the illustration in Fig. 2, at least one of the axles 125-135 is mounted relative to a chassis by means of a pneumatic spring element 235. A third sensor 230 can be provided here to determine the vertical distance of the chassis from the ground 140. One of the axles 125-135 can be raised pneumatically so that a wheel attached to it loses contact with the ground.This can be used to reduce rolling resistance under light loads or to assist maneuvering in tight spaces. An axle 125-135 can also be raised to increase the contact force of the trailer 110 on the axle acted upon by the drive motor 205. The lifting can be controlled to counteract wheel slippage on the first axle 125, for example, when there is a low coefficient of friction between the wheel and the ground 140.

[0045] Furthermore, an interface 240 is provided, via which signals can be exchanged between the tractor unit 105 and the trailer 110. The interface 240 can transmit one or more analog or digital signals. Examples of signals include a driving speed, a braking request, a reversing signal, or a torque request to a drive motor of the tractor unit. Transmission is typically electrical, but can also be wireless.

[0046] Fig. 3 shows a flowchart of an exemplary method 300 for controlling a trailer 110. It should be noted that the described steps do not necessarily have to be performed in the specified or illustrated order and that in some embodiments not all of the illustrated steps are implemented.

[0047] In a step 305, signals provided by the tractor unit 105 can be determined that indicate a driving state of the vehicle combination 105, 110. Thus, in a step 310, it can be determined whether forward travel or reverse travel is intended. During reverse travel, a signal is typically set to activate a reversing light on the trailer 110.

[0048] In a step 315, it can be determined whether a driving stability signal from the tractor unit 105 is present. This signal can also be called a VDC signal or VDC active signal and indicates that a wheel brake of the tractor unit is activated to influence the driving dynamics of the semi-trailer combination. A torque or speed requirement for a drive motor of the tractor unit 105 can be reduced at the same time. The tractor unit 105 can have various driving assistants, each of which can trigger such an intervention, for example, an anti-lock braking system (ABS) and an electronic stability program (ESP). The determined signal can allow a direct conclusion to be drawn about which stability program is active. Alternatively, the currently active program or the current driving situation can be deduced based on further observations.In particular, it can be determined that the driving stability signal at a driving speed close to zero—especially when starting off or driving uphill—indicates a slipping wheel of the tractor 105. The wheel may slip, in particular, because the coefficient of friction with the ground 140 is too low, an incline being traveled is too steep, or the mass of the trailer 110 is too large.

[0049] In a step 320, the enablement of the uphill start assist proposed herein can be detected. The enablement can be controlled manually by a driver of the tractor unit 105. If the enablement is present, the assistance for an uphill start can be controlled automatically by the drive unit 210. If the enablement is not present, assistance can be prevented or an ongoing assistance can be aborted. Optionally, the signal can also relate to an explicit request for assistance. The driver can thus express a desire for assistance during a start. In response to this desire, the assistance can be controlled with reduced conditions or with increased effect. For example, the assistance can also be controlled on a lower gradient than intended or even on level ground.A maximum drive torque provided or a maximum driving speed up to which assistance is provided may be increased.

[0050] In a step 325, a braking signal can be detected, which can relate to a service brake or a parking brake of the trailer 110. If this signal is detected, the assistance by the drive motor 215 can be quickly deactivated. A braking system can be activated independently to brake a wheel on one of the axles 125-135. Furthermore, conditions on board the trailer 110 can be checked. In a step 340, an incline of the ground 140, in particular as an incline in the direction of travel or in the towed direction, can be determined. Optionally, a gradient in the direction of travel is determined.

[0051] In a step 345, a mass of the semi-trailer 110 can be determined. The mass can be determined based on an axle load, which can be determined, for example, based on a pneumatic pressure in a pneumatic spring element 235. Furthermore, a bearing load of the semi-trailer 110 on the tractor 105 can be determined. The mass can also have been determined during a previous journey, in particular based on a detected tractive force and an acceleration achieved during this journey, or based on a detected deceleration force and a deceleration achieved during this journey. A prevailing gradient or incline, which can be detected by the third sensor 230, can be taken into account.

[0052] A tractive force on the trailer 110 can be determined in a step 350. As described, an on-board sensor can be used for this purpose. A tractive force can also be received from the tractor 105 via the interface 240. Optionally, the tractive force can be determined multiple times, and the measured values ​​can be compared or compared against each other.

[0053] In a step 355, a travel speed of the semi-trailer 110 can be determined. The travel speed relates to a movement over the ground 140, whereby it is particularly possible that only a component in the direction of the determined tractive force is taken into account.

[0054] In a step 360, a coefficient of friction between a wheel of the semi-trailer 110 and the ground 140 can be determined. The coefficient of friction can be determined, for example, based on a drive torque and a slip behavior of a wheel driven by the drive engine 205. Alternatively, a coefficient of friction provided via the interface 240 can also be used. In a step 380, based on collected information, it can be determined that a driving situation exists that corresponds to starting on a slope, in particular on an incline. This can be the case if a driving speed falls below a predetermined threshold and, at the same time, an incline in the direction of the tractive force or the direction of travel of the semi-trailer 110 exceeds a predetermined threshold. Furthermore, it can be determined that the tractive force exceeds a predetermined threshold.

[0055] In response to the specific driving situation, in a step 385, the electric motor 210 can be controlled to assist the starting process by driving a wheel of the trailer 110 to generate propulsion. The amount of the drive torque or drive force can be determined depending on prevailing conditions. For example, the drive torque can depend on the mass of the trailer or the degree of the specific gradient. Furthermore, a specific coefficient of friction with the ground 140 can be taken into account.

[0056] Reference symbol (as part of the description)

[0057] 100 semi-trailer trucks

[0058] 105 tractor

[0059] 110 trailers

[0060] 115 steered axle

[0061] 120 drive axle

[0062] 125 first axle

[0063] 130 second axle

[0064] 135 third axle

[0065] 140 Underground

[0066] 200 control device

[0067] 205 electric drive machine

[0068] 210 Energy source

[0069] 215 Interface

[0070] 220 first sensor

[0071] 225 second sensor

[0072] 230 third sensor

[0073] 235 pneumatic spring element

[0074] 240 interface

[0075] 300 procedures

[0076] 305 Determine tractor signals

[0077] 310 Reverse

[0078] 315 VDC signal

[0079] 320 release

[0080] 325 Braking

[0081] 340 Determine inclination

[0082] 345 Determine mass

[0083] 350 Determine pulling force

[0084] 355 Determine driving speed Determine friction coefficient Determine starting on a slope Control electric drive motor

Claims

Patent claims 1 . A method (300) for controlling an electric drive motor (205) on a semi-trailer (110), wherein the semi-trailer (110) is configured to be pulled by a tractor (105); wherein the method (300) comprises the following steps: - determining (350) a tractive force acting on the semi-trailer (110); - determining (355) a driving speed of the semi-trailer (110); - determining (340) an inclination of a ground (140) of the semi-trailer (110); - determining (380), on the basis of the tractive force, the inclination and the driving speed, that the semi-trailer (110) should be driven uphill; and - Controlling (385) the drive motor (205) to assist starting by a drive torque.

2. Method (300) according to claim 1, wherein a predetermined course of the tensile force is determined which indicates a start.

3. Method (300) according to claim 1 or 2, wherein it is determined on the basis of a profile of the tractive force and a profile of the driving speed that a drive wheel of the tractor (105) is slipping.

4. The method (300) according to any one of the preceding claims, wherein it is determined that a drive wheel of the tractor (105) is slipping based on the driving speed and a VDC signal of the tractor (105).

5. Method (300) according to one of the preceding claims, wherein the drive torque is controlled as a function of a mass of the semi-trailer (110).

6. Method (300) according to one of the preceding claims, wherein the drive torque is controlled as a function of a degree of inclination.

7. The method (300) according to any one of the preceding claims, wherein the assistance is terminated when a braking request from the tractor (105) is detected.

8. The method (300) according to any one of the preceding claims, wherein the starting is terminated when the driving speed exceeds a predetermined threshold value.

9. Method (300) according to one of the preceding claims, wherein the drive torque is controlled as a function of a coefficient of friction of a wheel driven by the drive motor (205) on the ground (140).

10. A control device (200) for a semi-trailer (110) adapted to be pulled by a tractor (105); wherein the semi-trailer (110) comprises an electric drive motor (205) for providing a drive torque; wherein the control device (200) comprises: - a first sensor (220) for determining a tractive force acting on the trailer (110); - a second sensor (225) for determining a driving speed of the semi-trailer (110); - a third sensor (230) for determining an inclination of a ground (140) of the semi-trailer (110); wherein the control device (200) is configured to - to determine, on the basis of the determined tractive force, the determined driving speed and the gradient, that the semi-trailer (110) should be driven uphill; and - to control the drive machine (205) to provide a drive torque to the wheel.

11. A semi-trailer (110) adapted to be pulled by a tractor (105), comprising an electric drive motor (205) for providing drive torque; and a control device according to claim 10.

12. A semitrailer (100) comprising a semitrailer (110) according to claim 11 and a tractor (105).

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