SE1250681A1 - Method and control unit for controlling a regenerative braking system in a vehicle - Google Patents

Abstract

The method and a control unit for controlling a regenerative brake system in a vehicle for which there is a defined maximum speed vmax which the vehicle should not exceed are presented. According to the present invention at least one predicted speed vpred for the vehicle on a section of road is determined. If the at least one predicted speed vpred exceeds the maximum speed vmax along the section of road, the regenerative brake system is then activated before an actual speed vact of the vehicle reaches the maximum speed vmax. The result is braking over more time and with less power than in previous known solutions, making it possible for the regenerative brake system to utilise more of the brake energy than in previous known systems.

Description

l0 l5 20 25 30 the vehicle, for example by using a brake pedal, if the speed of the vehicle exceeds the maximum speed vmm.

Many motor vehicles today are equipped with cruise control. One goal of cruise control is to achieve an even predetermined speed. Cruise control is often performed in vehicles by two cooperating systems, a cruise control system, which requests engine torque from an engine system, and a constant speed braking system, which prevents the vehicle from rolling up at too high a speed, especially on downhill slopes.

The cruise control tries to adjust the engine torque to avoid deceleration, or application of braking action, on the downhills where the vehicle accelerates by its own weight. An overall goal for the cruise control is to provide a comfortable driving and increased comfort for the driver of the motor vehicle, since the driver does not have to apply gas for the vehicle to keep a speed set speed selected by the driver. The set speed v fi m is the speed that the driver wants the motor vehicle to keep on a level road and which is set by the driver.

The cruise control then provides an engine system in the vehicle with the set speed v fifi for controlling the engine system. The set speed vxü is often related to a speed limit for a road section where vehicles are located.

A traditional constant speed brake automatically brakes the vehicle when a Down Hill Speed Control (DHSC) vmßc has been reached. The constant speed braking speed vmmc is often related to the set speed wet for the cruise control with an offset, in that the constant speed braking speed vüwc is equal to the set speed wet plus the offset speed v fi fat, vmwc = wet + v væ fat. When the constant speed brake is used, the maximum speed vmm corresponds to the constant speed brake speed vmßc, vmm = vüßc.

The constant speed brake thus regulates the speed of, for example, heavy vehicles on downhill slopes, as these accelerate by their own weight on the downhill slopes.

The constant speed brake control uses auxiliary brakes, which may include, for example, a retarder, an exhaust brake, and a four-stage electromagnetic brake (Telma), or a hybrid system comprising an electrical device which acts as a brake when used in a generator mode of the device. Other types of brakes can also be used by the constant speed brake.

Brief description of the invention For conventional vehicles, constant speed braking or driver-controlled braking, for example with a brake pedal, usually constitutes a complete loss. Constant speed braking and driver-controlled braking are often related to the above-mentioned maximum speed wwx.

For vehicles comprising a regenerative braking system, some of the total braking energy can be recovered. How large this recyclable part is depends, among other things, on the size of the braking energy and / or the braking energy, as well as on other parameters specific to the regenerative braking system.

In this document, the invention will mainly be described in relation to constant speed braking, but a person skilled in the art realizes that corresponding effects and problems that occur with constant speed braking can also occur with driver-controlled braking. The principles of the present invention can be applied to substantially all chord cases where one can be allowed to choose when the braking action is to be applied. Thus, if it is not critical from a safety perspective exactly when the vehicle is to begin braking, so that this time can be controlled by the control unit according to the present invention, then the present invention can be applied. One such application example is downhill braking.

The present invention can be realized on substantially all types of vehicles including a regenerative braking system.

Vehicles with regenerative braking systems include hybrid vehicles and all-electric vehicles.

A regenerative braking system can be an integral part of a vehicle's driveline. As an example, it can be mentioned here that hybridized vehicles, where an electric machine is controlled in generator mode during braking, whereby the braking energy is at least partially utilized.

Regenerative braking systems may include one or more of a battery, a supercapacitor, a flywheel, a spring, a hydraulic pump cooperating with an accumulator, a pneumatic compressor cooperating with a pressure tank, and a device for transferring energy to a consumer in the vehicle. These devices recover or transfer the energy that is slowed down by the braking system. When the energy is transferred to consumers in the vehicle, loads can be controlled to consume the energy during braking. A well-functioning regenerative braking system can, under favorable conditions, recover a significant part of the braking energy.

Prior art constant speed brakes base their function on how an actual speed wax of the vehicle is related to the constant speed braking speed vüwc in such a way that the braking effect is applied when the constant speed braking speed vmßc has been reached.

The braking action is then continued to be applied so that the constant braking speed vüßc is maintained. These braking often causes relatively large energy to be slowed down under high power, which is seldom optimal from a regeneration perspective. In other words, prior art constant speed brakes can waste energy, as the energy is slowed down with such a high power that not all of this braking energy can be taken care of by the regenerative braking system, which means that traditional braking systems must also be used. Thus, the level of power to be taken care of by the regenerative braking system in prior art systems is not optimal for regeneration.

There are mainly two reasons why high effects are not optimal during regeneration. One reason is that the regenerative braking system has a maximum power, which means that conventional braking systems must be used if the required braking power is higher than this maximum power. Another reason is that the efficiency of regeneration is lower at higher effects.

Taken together, today's known constant-speed braking systems provide non-optimal regeneration in the braking system, as they do not take into account regeneration-related properties of the driveline and / or braking system.

It is therefore an object of the present invention to provide a control which provides a more energy efficient regenerative braking system.

This object is achieved by the above-mentioned method for controlling a regenerative braking system according to the characterizing part of claim 1. The object is also achieved by the above-mentioned control unit according to the characterizing part of claim 28, and by the above-mentioned computer program and computer program product.

The present invention controls when, i.e. at what time / position, the regenerative braking system is to be activated to provide a favorable regeneration in the driveline. If this time / position is selected according to the invention, this time / position is brought forward compared with previously known systems, which means that braking can take place for a longer period of time. This reduces the average power for braking, as the energy to be braked is distributed over a longer period of time. As a result, the regeneration takes place at a lower average power, whereby a larger part of the braking energy can be utilized by the regenerative braking system compared with previously known systems. Thus, the control of the braking is adapted to the regenerative braking system's possibilities to recover the braking energy. In other words, regeneration is optimized based on the regenerative properties of the regenerative braking system to enable a higher degree of energy recovery.

Utilizing a lower braking effect, i.e. by braking over a longer period of time according to the invention, means that a larger part of the braking can be done with the regenerative braking system compared to previously known braking with a higher braking effect. This is advantageous because no energy is recovered when braking with traditional braking systems. Even lower fuel consumption is obtained with the present invention, since the recovered energy can later be used to relieve, for example, an internal combustion engine in the vehicle, or to drive other consumers in the vehicle.

The present invention can thus take care of and utilize a larger part of the total braking energy with the regenerative braking system than previously known systems, since a larger part of the braking power is below the maximum power for the regenerative braking system. Although the braking power with prior art brake control is below the maximum power of the regenerative braking system, the efficiency of the regenerative braking system can increase if the present invention is used. A larger part of the braking energy is thus taken care of by utilizing the present invention, both for braking effects above and below the maximum effect.

The time / position for activating the braking action can in favorable cases be chosen so that the regenerative braking system can utilize essentially all braking energy. In this way, essentially no energy is wasted on pure deceleration of the energy, since essentially no traditional braking systems are used to reduce the speed of the vehicle.

In addition, a reduced average speed, which is the result of an extension of the braking period according to the invention, also has the effect that the air resistance to the vehicle becomes lower. This means that less energy is slowed down by the air resistance, which in turn means that more energy can be slowed down by the regenerative braking system. In this way, a larger part of the braking can be done by the regenerative braking system where it is possible to recover the energy. Therefore, with the present invention, some of the energy previously braked by the air resistance can be recovered through the regenerative braking system.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be further elucidated below with reference to the accompanying drawings, in which like reference numerals are used for like parts, and in which: Figure 1 shows a flow chart incorporating the method of the present invention, Figure 2 shows an example of a case, Figure 3 shows a example of a driving case, Figure 4 shows an example of a driving case, and Figure 5 shows a control unit.

Description of Preferred Embodiments Figure 1 shows a flow chart incorporating the method of the present invention. In a first step 101 of the method, at least one predicted speed Vpæd is determined, which the vehicle is predicted to follow during a road section. The at least one predicted speed vpæd is thus determined here for a period of time which the vehicle will spend on the road section. The road section extends closest in front of the vehicle and can here, for example, have a length L which is 1000 meters, or can have another arbitrary suitable length.

The determination of the at least one predicted velocity vpæd can be determined here in a number of ways, and based on a number of parameters, which will be described in more detail below.

For the vehicle, there is a maximum speed vmm defined that the vehicle should not exceed. In a second step 102 of the method of the present invention, a regenerative braking system is activated in the vehicle if the at least one predicted speed Vpmd exceeds the maximum speed vmm below the road section, and the activation of the regenerative braking system according to the invention takes place before an actual speed of the vehicle reaches the maximum the speed vmm. In a third step 103 of the process, braking energy is recovered in the regenerative braking system when the braking action is applied.

Thus, in the second method step 102, it is analyzed whether the at least one predicted speed vpæd determined in the first method step will exceed the maximum speed vmm below the road section. If this happens, the actual speed at which the vehicle is driven is compared with and the maximum speed vmn to determine when the actual speed of the vehicle will reach the maximum speed vmm. Then the regenerative braking system is activated before the actual speed what reaches the maximum speed vm fl.

In previous kanda systems, only the actual speed wax has been compared with the maximum speed vmm, and when the actual speed væï has exceeded the maximum speed vmm, the braking has been activated. According to the present invention, the stall is first identified if braking will be relevant based on the predicted speed Vpma.

Then this knowledge is used to advance the activation of the regenerative braking system compared to previous kanda systems, that is to say to select an activation position PKÜÜH which occurs before the actual speed waxes when the maximum speed vm fl. As a result, braking is achieved over a longer period of time, which results in a lower braking effect during braking and thereby a larger part of the braking energy can be utilized by the regenerative braking system than with previously known systems.

The prior art method and the method of the present invention are schematically illustrated in the unrestricted example of Figure 2. A vehicle will have to descend a downhill slope at a first position P1. According to previous known solutions, the actual speed v¿m_ægwÄr would have increased on the downhill slope due to the train's train weight M, until it reaches the defined maximum speed mmx at a second position P2. Only when the actual speed væï¿E @ ¿M when the defined maximum speed vmm is activated according to previous solutions braking. Then the actual speed v¿æ_K fl must remain at the level of the maximum speed vm fl until the downhill slope is passed at a third position P3 and the vehicle starts to drop at 10 15 20 25 30 10 speed again. The vehicle is finally back to its original speed at a fourth position P4. According to the prior art, the vehicle is braked here between the second position P2 and the third position P3.

According to the present invention, the at least one predicted speed vpmd for the road section in front of the vehicle is determined. The predicted speed vpæa is then analyzed to see if it will exceed the maximum speed vmm if no braking takes place. In this example, it is stated that the predicted speed Vpma would exceed the maximum speed vm fl at the second position P2 if no braking is performed. Therefore, according to the invention, the braking will be activated in an activating position PKÜHU which is before the second position P2 when the actual speed according to the invention wax would have reached the maximum speed vmm if no braking had been performed. According to the invention, braking action is applied until the third position P3 is reached. At a merging position Pwmmn, which is after the second position P2, the actual speed according to the invention will coincide with the previously known actual speed Vact_regular - As shown in Figure 2, the actual speed which according to the present invention will be below the actual speed vaüénmm fi r according to previously known solutions, from the activating position Pmg to the co-joining position Pwmmn, which means that the average velocity of the actual wax velocity according to the present invention is lower than the actual velocity of wax according to prior art solutions. The braking action is applied with the present invention from the activating position Pn 2 to the third position P3, which prolongs the braking time by the interval between the activating position Pmqw and the second position P2 compared to the prior art. This meant that braking takes place over a longer distance / time period and with a lower braking effect than for previously known solutions.

In this way, the braking effect can be regulated to a level that is more favorable for regeneration with the regenerative braking system, whereby a larger part of the braking energy can be utilized by the regenerative braking system than with previously known systems.

Here and in this document, the invention has been described by means of positions, such as the positions P1, P2, P3, P4, Pæq fi, and Pwmmn. However, it will be appreciated by those skilled in the art that these positions have equivalents in times.

The magnitude of the maximum speed vm fl can be determined in several different ways. If the vehicle is equipped with a cruise control, where for example the driver sets a desired set speed v fifi, the maximum speed vm fl can have a magnitude related to the set speed wet. According to an embodiment of the invention, the maximum speed vm kan can exceed the set speed wet by a number of X percent, vmax == væ¿ * (1-tïâ fi.

Since the driver often sets the set speed related to a speed limit for the road section, the maximum speed vmm here is also often indirectly linked to a speed limit for the road section.

According to one embodiment of the invention, the maximum speed vmm is related to a constant speed braking speed væßc for a constant speed brake in the vehicle. The maximum speed can here be set equal to the constant speed braking speed vüwc, ie vm fl = vüßc.

In this way, the embodiment provides a coupling to the constant speed brake and its use on downhill slopes. 10 15 20 25 30 12 The magnitude of the maximum speed vm fl can also be related to how the driver behaves when he drives the vehicle.

For example, if the driver often starts to brake the vehicle at a certain driver-dependent speed vm3M¿mjW¶ on downhills, the system learns that the maximum speed vm fl should be set to this value, ie vmm = vmHR¿mjW¶. The system is thus adapted to the driver's behavior and if the driver, for example, starts to brake at a lower speed on downhill slopes than before, the value of the driver - dependent speed vbmkåßnya will decrease.

According to one embodiment, the magnitude of the maximum speed vmm is related to what the road section and / or the traffic on it looks like. Thus, one or more properties of the road section determine the magnitude of the maximum speed vmm, where such properties may include a speed limit, or a curvature of the road section.

In addition, the characteristics may include the presence or absence of one or more speed cameras and how the traffic situation is on the road section, ie for example if there is a queue on the road section or not.

Since the maximum speed vmm is related to ambient traffic on the road section, radar can be used to determine a speed of and / or a distance to a vehicle in front. Then the maximum speed vmm can be determined in such a way that the vehicle does not risk driving into, or getting too close to, the vehicle in front. Radar is used, among other things, by adaptive cruise control (ACC), which means that radar information is available in vehicles equipped with such adaptive cruise control. Therefore, the contribution in complexity becomes very modest for this embodiment. According to an embodiment of the invention, the maximum speed vmm may vary in size during said road section. In other words, the maximum speed vmm is dynamic. The magnitude of the maximum speed vmn can here be a function of, for example, the time or positions in the road section. The maximum velocity vm fl can then, for example, consist of a vector with possibly different values corresponding to different times / positions.

According to an embodiment of the present invention, the predicted speed vpæd is determined based on a knowledge of the road section. This knowledge may be based on one or more of the positioning information, such as GPS information (Global Positioning System information), map information, topography information, weather reports, information communicated between different vehicles and information communicated via radio, and may consist of knowledge of prevailing topography, curvature, traffic situation, wave work, traffic intensity and road conditions. Furthermore, the knowledge can consist of a speed limit for the upcoming road section, as well as a traffic sign adjacent to the road. Today, many vehicles include systems, such as navigation systems and cruise control systems, which utilize such information. Therefore, this embodiment can be implemented with a low addition in complexity in vehicles where the information is already available.

Figure 3 shows a non-limiting example of utilization of knowledge about the road section for the same driving case as shown in figure 2.

The actual speed is * mqw @ r and the braking sand according to the prior art corresponds to that described for Figure 2 OVEBII.

According to the embodiment of the present invention where knowledge of the road section is present, the at least one predicted speed Vpm fl is determined taking into account this knowledge. The predicted velocity Vpma in the figures largely corresponds to the curve for the actual velocity vam_ægmÄr according to the prior art. Since the control unit that performs the determination of the predicted speed Vpma then has very good knowledge of what the road section looks like in the future, a very accurate determination of the predicted speed vpæd can be made.

Based on this very accurately predicted speed vpæd, braking can be determined so that the energy recovery for the regeneration in the regenerative braking system is maximized while the vehicle maintains a suitable actual speed vam at the end of the downhill slope. In addition, braking can be started earlier because the control unit can predict with great certainty that the actual speed of wax will exceed the maximum speed vm fl if no braking takes place.

This is illustrated in the example in Figure 3, where the at least one predicted speed Vpæd for the road section in front of the vehicle is determined and analyzed to see if it will exceed the maximum speed vm fl if no braking takes place. The predicted velocity Vpma here corresponds, as mentioned above, largely to the curve of the actual velocity growth according to the prior art. Since the control unit knows that the predicted speed Vpma is reliable, it can already apply the braking effect at the beginning of the downhill slope, i.e. at the first position P1. Thus, here the activation position Pmqw coincides with the first position P1, Pæqw = P1, which is located before the second position P2 when the actual speed according to the invention would have reached the maximum speed vmm if no braking had been performed. The second position P2 is also the position when previously known solutions would have started to apply the braking effect. According to this embodiment, the braking effect can thus be applied directly when the vehicle begins to accelerate on the downhill slope, since this acceleration based on the knowledge of the road section can easily be predicted to reach the maximum speed vm fl.

According to the invention, braking action is applied until the third position P3 is reached. In this example, the third position P3 coincides with the concomitant position Pwmmn, Pwmmn = P3, at which the actual velocity according to the invention wax and the previously known actual velocity væï¿E @ ¿a coincide again.

As can be seen from Figure 3, the actual velocity v @ in the present invention is below the actual velocity v in the prior art solutions for a relatively long time, from the activating position Pmqmlt to the co-joining position Pwmmn. As a result, the average velocity of the actual velocity of the present invention is lower than the average velocity of the actual velocity of prior art solutions during the same period, which begins at the first position P1 and ends at the third position P3.

The braking action is applied with the present invention from the activation position Pægalt to the third position P3, which prolongs the braking distance / braking time by the interval between the first time position P1 and the second position P2 compared to the prior art. This means that braking takes place over a longer period of time and thus at a lower braking effect, whereby a larger part of the braking energy can be utilized than for previously known solutions. In addition, braking can be controlled with high precision so that the maximum speed vmm is reached just when the downhill slope ends to maximize the fuel savings for the vehicle. According to an embodiment of the present invention, a velocity profile vpmf extending from an actual velocity wax, for example the actual velocity bet at the first position P1, is determined to the maximum velocity vm fl, for example at the third position P3 . In the example of Figure 3, then, the velocity profile vpmf could correspond to the dashed line of the actual velocity wax of the present invention between the first P1 and third P3 positions. Thus, the appropriate velocity profile vpmf here can first be determined, after which the activation of the regenerative braking system is done based on the velocity profile vpmf. The appropriate shape of the speed profile vpmf may depend on which parameter is to be optimized, for example it may depend on fuel economy, regeneration, driver acceptance, co-traffic acceptance, and / or driver comfort.

According to one embodiment, the velocity profile vpmf is determined so that the resulting braking power has a value which is within a favorable range for the regenerative braking system regeneration. so that the resulting braking power is below this braking power limit.

There are strategic cruise controllers, such as the “Look Ahead” cruise control (LACC), which use knowledge of the sections of road ahead, ie knowledge of what the road will look like in the future, to determine the appearance of a reference speed vn fi in such cruise control an engine system is provided. in the vehicle for controlling a torque request from the engine. In strategic cruise control, the reference speed vn ts is allowed, within a speed range, to differ from the set speed chosen by the driver wet to achieve a more fuel efficient driving based on the knowledge.

The knowledge can be used by the LACC in a variety of ways. For example, knowledge of an upcoming speed limit for the road can be used to achieve fuel-efficient speed reductions prior to an upcoming lower speed limit.

Correspondingly, knowledge of, for example, an upcoming roundabout or intersection can also be used to brake in a fuel-efficient manner before the roundabout or intersection.

For example, a LACC allows the reference speed weave to be raised in front of a steep uphill slope to a level which is above the level of the set speed weave, since the motor vehicle is assumed to lose speed on the steep uphill slope due to high train weight relative to the vehicle's engine performance. Similarly, the LACC allows the reference speed of the web to be lowered to a level which is below the set speed wax in front of a steep downhill slope, since the motor vehicle is assumed to accelerate on the steep downhill slope due to the high train weight. The idea here is that it is more fuel efficient to use the motor vehicle's acceleration due to its own weight on the downhill slope than to first accelerate downhill and then brake downhill. In this way, the LACC can reduce fuel consumption while largely maintaining driving time.

Figure 4 shows a non-limiting example of how an embodiment of the present invention may interact with a LACC. The actual speed væï¿f @ fl æ; and the braking sand according to the prior art corresponds to that described for Figures 2 and 3 above. Those skilled in the art will appreciate that, in addition to the downhill case shown in Figure 4, the invention may also be utilized in connection with other speed changes initiated by the LACC.

According to the embodiment of the present invention where knowledge of the road section is present, and a collaboration with LACC is utilized, the predicted speed Vpæa is determined taking into account the knowledge possessed by LACC. As mentioned above, in some cases the LACC lowers the reference speed vmf to a level below the set speed wet, for example facing a downhill slope, as it reduces the need for conventional braking and is fuel-efficient.

If the LACC indicates that it intends to reduce the actual speed of wax, for example before a downhill, then, as shown in Figure 4, braking action can be applied in an activation position Praæn even before the downhill starts in the first position P1. Thus, regeneration can be performed by the regenerative braking system as the lowering of the actual speed wax is done before the downhill, which means that the braking time is further extended. Compared with previously known solutions, by utilizing this embodiment of the invention, the braking time and the braking distance are increased by the interval from the activating position Pæg1 to the second position P2 when the previously known solutions had started to brake.

Then the regeneration can continue for the braking during substantially the entire downhill until the actual speed wax according to the present invention reaches the maximum speed vm fl and also coincides with the actual speed v¿ü_ægm fi r according to previously known solutions in the third position P3 at the end of the downhill, where P3 = PCOIIUHOH ° As shown in Figure 4, the actual velocity v @ 3 according to the present invention is at a level below the actual velocity v 3 in the previously known solutions for a long time, from the first position P1 to the merging position Pwmmn. As a result, the average speed, and also the braking effect, of the actual speed wax according to the present invention has a lower value than the average value of the actual speed vamíægm fi r according to previously known solutions during the same period. In addition, regeneration can be performed from the fact that the actual speed væï according to the LACC is allowed to fall below the set speed vxü in the activation position Pæqw, which occurs before the descent begins in the first position P1.

The braking according to this embodiment therefore takes place over a longer distance and time period and gives a lower braking effect, whereby a larger proportion of the braking energy can be utilized by the regenerative braking system than with previously known solutions.

According to an embodiment of the present invention, in determining the predicted speed Vpma, it is assumed that the road slope below the road section is substantially equal to the road slope is where the vehicle is when the determination is performed. For this embodiment, there is no requirement for the vehicle to have access to map information, positioning information and / or topography information, since the road inclination where the vehicle is located can be determined based on another way, for example based on an accelerometer, or on a force equation. The road slope where the vehicle is located may also be available in the vehicle, as it is used by other systems, such as gear selection systems or the like. Therefore, this embodiment often adds a limited amount of complexity to the vehicle. According to one embodiment of the present invention, the determination of the predicted speed vpmd is based on the actual speed wax and on an actual acceleration aam of the vehicle. Then it is analyzed here how close to the vehicle's actual speed wax is the maximum speed vm fl, and how fast the vehicle approaches the maximum speed vm fl.

The activation position Pmqm is then also determined based on a difference between the actual speed wax and the maximum speed vmm, as well as on an actual acceleration aæï the vehicle.

For example, it may be considered appropriate to apply braking action if the actual speed of the vehicle is relatively close, and in addition rapidly approaching the maximum speed VmaX. According to one embodiment of the present invention, the determination of the at least one predicted speed vpæd is based on an assumption that the fuel supply to the engine is throttled for parts or the entire road section. The predicted speed vpm fl is based here on an engine brake simulation, where the engine torque is based on a towing of the engine, ie on a towing torque curve for the engine.

According to an embodiment of the present invention, the determination of the at least one predicted speed vpæd is based on an assumption that the vehicle is freewheeling for parts or the entire road section. The simulation of the predicted speed vpmd is based here on a freewheel simulation, where the vehicle is allowed to roll freely with open clutch and / or in neutral gear. When the vehicle is freewheeling, no power is transmitted from the engine to the drive wheels.

During cruise control driving, the driveline torque, i.e. the driving moment of the vehicle, is regulated by a speed controller in the vehicle, where the speed controller receives setpoints for the speed from the cruise control logic. For traditional cruise control, the set speed wet is such a setpoint. For cruise control where the reference speed vmf is allowed to deviate from the set speed v fi ü, such as for example LACC, the reference speed væf constitutes this setpoint.

According to an embodiment of the present invention, the determination of the at least one predicted speed vpæd is based on a cruise control simulation performed in the vehicle, where the cruise control simulation is based on a speed setpoint. In the case where the vehicle is driven with the cruise control switched on, the speed setpoint in the simulation can then be based on the set speed wet for the cruise control.

The setpoint can also be based on the vehicle's current actual speed growth, or on an estimate of a driver's desired actual speed growth. This embodiment provides an accurate estimate of the at least one predicted speed vpæd even when cruise control is not applied in the vehicle, i.e. when accelerating the pedal.

According to an embodiment of the invention, the activation position Pæqw is determined to a position when the vehicle accelerates and when it is determined that the predicted speed vpmd will exceed the maximum speed vmm. An example of such an activation position Pæqw is shown in Figure 2, where the vehicle is on a downhill slope and accelerates due to its train weight, while it can be determined that the predicted speed vpæd will exceed the maximum speed vmm.

According to an embodiment of the present invention, the activation position Pmqw, i.e. the position when the regenerative braking system is activated, is determined to the position when the vehicle has an excess force and when it is determined that the predicted speed vpæd will exceed the maximum speed vmm. A vehicle is considered here and in this document to have a surplus of power if it accelerates without fuel supply to the engine. An example of such an activation position Pmg fl is shown in Figure 2, where the vehicle is on a downhill slope and accelerates due to its train weight.

According to an embodiment of the invention, the activating position Pægült is determined to a position from which the maximum speed vm fl is calculated to be reachable during the road section by utilizing a braking energy which can be achieved with the regenerative braking system. An example of such an activating position Pæq fi is shown in Figure 3, where in the first position P1 it can be determined that the velocity profile vpmf can be realized by braking with the regenerative braking system so that the maximum speed vm fl is reached during the road section, for example at the third position P3 .

According to one embodiment of the present invention, the activation of the regenerative braking system is based on an adaptive algorithm. This algorithm analyzes how much braking energy needs to be braked away, where this braking energy changes dynamically during the vehicle's progress, among other things due to the vehicle's speed and on the road slope. Based on this dynamically changing braking energy, the braking action to be applied to brake this braking energy is then calculated adaptively.

The adaptive algorithm can here be based on at least one prediction of a braking process vpæ¿¿Kææ for the vehicle.

The braking process vpæ¿¿L fl e indicates here how the actual speed wax will be changed by the determined suitable braking effect.

According to one embodiment, the predicted braking sequence vpæd¿mææ is determined based on the current braking action, i.e. on the braking action applied when the prediction of the braking sequence vpæ¿¿xææ is made. According to another embodiment, the prediction of the braking process vm @ ¿pK & e changes dynamically during the braking itself. According to another embodiment, the predicted braking process vm3 @ pmke is determined based on a pre-calculated braking action, where this pre-calculated braking action has been calculated based on a suitable braking action to apply, where the suitability is judged based on a braking energy that needs to be braked away.

If the prediction of the braking process vmEQ¿n fl e, i.e. the prediction of how the actual speed wax for said vehicle will be changed by the determined suitable braking effect, will reach the maximum speed vmm increased braking effect, i.e. increased braking torque / braking effect. If instead the prediction of the braking process vpmqßr fl e shows that the actual speed growing for the vehicle will not reach the maximum speed vmm the braking effect is reduced, ie the braking torque / braking effect is reduced. The increase and / or decrease of the braking action can be determined here based on how close the maximum speed vmm the prediction of the braking process vpmd¿Kææ reaches. This results in a control which just reaches the maximum speed vmm at the end of the downhill slope.

Thus, according to these embodiments of the invention, a control of the braking system during the braking itself can be obtained, which results in a dynamic and more favorable regeneration with the regenerative braking system, since the braking effect can be regulated to a level which is more favorable for regeneration.

Those skilled in the art will appreciate that a method of controlling a regenerative braking system of the present invention may additionally be implemented in a computer program, which when executed in a computer causes the computer to perform the method. The computer program usually consists of a computer program product 503 (shown in Figure 5) stored on a digital storage medium, the computer program being included in a computer program readable medium of the computer program product.

Said computer readable medium consists of a suitable memory, such as for example: ROM (Read-Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable PROM), Flash memory, EEPROM (Electrically Erasable PROM), a hard disk drive, etc .

Figure 5 schematically shows a control unit 500. The control unit 500 comprises a calculation unit 501, which may be constituted by substantially any suitable type of processor or microcomputer, e.g. a Digital Signal Processor (DSP), or an Application Specific Integrated Circuit (ASIC).

The calculation unit 501 is connected to a memory unit 502 arranged in the control unit 500, which provides the calculation unit 501 e.g. the stored program code and / or the stored data calculation unit 501 is needed to be able to perform calculations. The calculation unit 501 is also arranged to store partial or final results of calculations in the memory unit 502.

Furthermore, the control unit 500 is provided with devices 511, 512, 513, 514 for receiving and transmitting input and output signals, respectively. These input and output signals may contain waveforms, pulses, or other attributes, which of the input signals receiving devices 511, 513 may be detected as information and may be converted into signals which may be processed by the computing unit 501. These signals are then provided to the computing unit 501. The devices 512 , 514 for transmitting output signals are arranged to convert signals obtained from the computing unit 501 for creating output signals by e.g. modulate the signals, which can be transmitted to other parts of the vehicle.

Each of the connections to the devices for receiving and transmitting input and output signals, respectively, may consist of one or more of a cable; a data bus, such as a CAN bus (Controller Area Network bus), a MOST bus (Media Orientated Systems Transport bus), or any other bus configuration; or by a wireless connection.

According to one aspect of the invention, there is provided a system comprising a control unit arranged to control a regenerative braking system in a vehicle. The control unit comprises a prediction unit, which is arranged to determine at least one predicted speed Vpma of the vehicle for a road section. This determination can be performed in a variety of ways according to the above-described embodiments of the method, the prediction unit being arranged so that it can perform the predictions according to the respective embodiment.

The control unit also comprises an activating unit, which is arranged to activate the regenerative braking system in the vehicle before an actual speed wax for the vehicle reaches the maximum speed vm fl and if the at least one predicted speed vmd exceeds the maximum speed vmm below the road section.

The control unit, and thus the system, according to the present invention has the same advantages as stated above for the methods according to the invention.

One skilled in the art will recognize that the above-mentioned computer may be the computing unit 501 and that the above-mentioned memory may be the memory unit 502. The person skilled in the art will also recognize that the above system may be modified according to the various embodiments of the method of the invention.

In addition, the invention relates to a motor vehicle 1, for example a truck or a bus, comprising at least one control unit for controlling a regenerative braking system according to the invention.

The present invention is not limited to the above-described embodiments of the invention but relates to and encompasses all embodiments within the scope of the appended independent claims.

Claims (28)

l0 l5 20 25 27 Patent claim A method for controlling a regenerative braking system in a vehicle for which a maximum speed vm fl, which said vehicle should not exceed, is defined, characterized in that a control unit performs the steps of: - determining at least one predicted speed Vpma for said vehicles for a section of road; and - if said at least one predicted speed vpæd exceeds said maximum speed vm fl during said road section, activate said regenerative braking system before an actual speed wax for said vehicle reaches said maximum speed vm fl. A method according to claim 1, wherein said road section comprises a downhill slope in which said vehicle accelerates due to a train weight M of the vehicle. A method according to any one of claims 1-2, wherein said maximum speed vm fl corresponds to a constant speed braking speed vüßc, vmm = vüwc, at which a constant speed braking system brakes the vehicle. A method according to any one of claims 1-2, wherein said maximum speed vm fl is related to a set speed væ fi of a cruise control. A method according to any one of claims 1-2, wherein said maximum speed vm fl is related to a preparatory behavior. A method according to any one of claims 1-2, wherein said maximum speed vm fl is related to ambient traffic for said road section. 10 15 20 25 28 A method according to any one of claims 1-2, wherein said maximum speed vm fl is related to a property of said road section. A method according to claim 7, wherein said feature comprises at least one in the group of: - a speed limit for said road section; - a curvature for said road section; - a presence of at least one speed camera at said road section; and - a traffic situation within said road section. A method according to any one of claims 1-8, wherein said maximum speed vm fl can be changed dynamically during said road section. A method according to any one of claims 1-9, wherein said road section extends immediately in front of said vehicle. A method according to any one of claims 1-10, wherein a knowledge of said road section is used in said determination of said at least one predicted speed Vpma. A method according to claim 11, wherein said knowledge is based on at least one information in the group of: - positioning information; - map information; and - topography information. A method according to any one of claims 1-10, wherein a road slope said vehicle experiences when said determination of said at least one predicted speed Vpma is performed is utilized in said determination of said at least one predicted speed Vmea. 10 15 20 25 30 29 A method according to any one of claims 1-10, wherein said determining said at least one predicted speed vpm fi is based on an actual speed v fi ï for said vehicle and on an actual acceleration aæï for said vehicle. A method according to any one of claims 1-14, wherein said at least one predicted speed vpmd is determined based on an assumption that a fuel supply to an engine in said vehicle is restricted for at least a part of said road section. A method according to any one of claims 1-15, wherein said at least one predicted speed is determined based on an assumption that said vehicle freewheels during at least a portion of said road section. A method according to any one of claims 1-15, wherein said at least one predicted speed vpæd is determined based on a cruise control simulation. A method according to any one of claims 1-17, wherein said activating said regenerative braking system is performed at a position in the group of: - an activating position Pæg fl w at which it is determined that said at least one predicted speed vpmd will exceed said maximum speed vmm and at which said vehicle accelerates; an activating position Pæqw, in which it is determined that the at least one predicted speed vpæd will exceed the maximum speed vm fl and in which said vehicle has a surplus of power, said vehicle accelerating without an engine in said vehicle being supplied with fuel; and - an activating position Pæqw, from which said maximum speed vmm is calculated to be reachable under said road section 10 by means of a braking energy which can be realized with said regenerative braking system. A method according to any one of claims 1-18, wherein said activation of said regenerative braking system is done based on a speed profile vpmf, which extends from an actual speed wax for said vehicle to said maximum speed vm fl. A method according to any one of claims 1-18, wherein the activation of said regenerative braking system is done based on an adaptive algorithm, which adaptively calculates a suitable braking action to apply based on a braking energy which needs to be braked away. The method of claim 20, wherein said adaptive algorithm comprises a prediction of a braking sequence vmÉ¿PR & e for said vehicle, which depends on said suitable braking action. A method according to claim 21, wherein said suitable braking action is increased if said prediction of said braking process vmæ @ pn fl e reaches up to said maximum speed Vmax - A method according to claim 21, wherein said suitable braking action is reduced if said prediction of said braking progress vpæd¿am is always lower than said maximum speed vm fl. A method according to any one of claims 21-23, wherein said predicted braking sequence vmatmam is based on one in the group of: - a current braking action; - a braking effect varying during braking; and - a pre-calculated braking action, which is based on a suitable braking action to be applied, wherein an assessment of whether said braking action is suitable is based on a braking energy which needs to be braked away. A method according to any one of claims 1-24, wherein said regenerative braking system comprises at least one device in the group of: - a battery; - a supercapacitor; - a flywheel; - a feather; - a hydraulic pump cooperating with an accumulator; - a pneumatic compressor cooperating with a pressure tank; and - a device for transmitting energy to consumers in said vehicle. A computer program comprising program code, which when said program code is executed in a computer causes said computer to perform the method according to any one of claims 1 to 25. A computer program product comprising a computer readable medium and a computer program according to claim 26, wherein said computer program is included in said computer readable medium. A control unit arranged for controlling a regenerative braking system in a vehicle, for which a maximum speed vmw which said vehicle should not exceed, is defined, characterized by: - a prediction unit, arranged to determine at least one predicted speed Vpma for said vehicle for a road section; and - an activating unit, arranged that, if said at least one predicted speed vpæd exceeds said maximum speed vmm during said road section, activating said 32 regenerative braking systems before an actual speed wax for said vehicle when said maximum speed vmm.