Method and device for determining energy consumption when driving a vehicle

Abstract

Method for determining a measure of energy use during operation of a vehicle (100), - which is equipped with a first energy source (101) for generating a first driving force for driving the vehicle (100) in a first direction of travel and with at least one first braking system, - which can be actuated to apply a first braking force acting against the movement of the vehicle (100) in the first direction of travel, and - which has an energy source for generating regenerative braking force acting on at least one wheel of the vehicle (100), wherein for a first period of time in which the request for motive power from the first energy source is interrupted, the method comprises: - estimating the energy consumption during operation of the vehicle (100) without requesting braking force from the first braking system, and - using the estimated energy consumption during operation of the vehicle (100) without requesting braking force from the first braking system as a basis for determining a measure of energy use during operation of the vehicle (100), characterized in that the procedure further comprises: - Compare energy consumption during operation without a demand for braking force from the first braking system and then when the demand for driving force from the first energy source is interrupted, with the energy consumption during regenerative braking; - using the comparison as a basis for determining a measure of the energy use of stored energy of the vehicle (100) during operation of the vehicle (100) for presenting this measure to the driver of the vehicle (100) via a display.

Description

Field of the invention

[0001] The present invention relates to a method for use during the operation of a vehicle. In particular, the invention relates to a method for determining energy usage during the operation of a vehicle according to the preamble of claim 1. It also relates to a system and a vehicle, as well as a computer program and a computer program product, that implement the inventive method. General state of the art

[0002] The following description of the general state of the art represents a description of the general state of the art for the invention and therefore does not necessarily represent the state of the art.

[0003] Vehicles in general, and at least to some extent heavy-duty vehicles in particular, are the focus of ongoing development efforts to improve fuel economy and reduce exhaust emissions. Factors such as increasing public concerns about pollution and air quality, for example, in urban areas, have led to the adoption of emissions standards and regulations in many countries.

[0004] When operating heavy-duty vehicles such as trucks, buses, and the like, the impact of efficient vehicle operation on the profitability of the industry in which they are used has also increased over time. In addition to the purchase price of a vehicle, the main expenditure items for its ongoing operation are driver wages, repair and maintenance costs, and fuel. It is therefore important to try to reduce costs in each of these areas as much as possible.

[0005] One area where developments are being driven, at least in part, by efforts to reduce emissions and fuel costs is hybrid vehicles. Hybrid vehicles utilize two or more power output and / or fuel sources, and a common type of these vehicles is the hybrid electric vehicle, in which one or more electric machines can be used to generate power to the vehicle's drive wheels.

[0006] The electric machine offers the advantage that electrical energy can be converted into driving power with a relatively high degree of efficiency. This power can also be used simultaneously to apply braking force to the vehicle's drive wheels, thereby harnessing the kinetic energy they absorb to recover electrical energy, which can then be fed back into the vehicle's electrical system and, in particular, into an energy storage device. The recovered energy can then be reused by the electric machine to generate driving power.

[0007] Hybrid vehicles thus represent an opportunity to reduce fuel consumption, but it is also very important that they are driven economically by their drivers, as the driving style of a vehicle can have a very significant impact on overall fuel savings. This has led to the development of systems designed, for example, to help drivers and owners assess whether vehicles are actually being driven in a fuel-efficient manner. However, the most advantageous driving style for a vehicle such as a hybrid vehicle, e.g., from a fuel savings perspective, is not always obvious to the driver.

[0008] Document US 2012 / 0 283 940 A1 discloses a solution for the variable display of operating costs in the form of dynamic fuel costs. These are calculated based on a detected operating state of the vehicle and continuously displayed to the driver.

[0009] The document US 2012 / 0 179 346 A1 discloses a solution for indicating braking efficiency in which a total recovered regenerative braking energy is compared either with a maximum possible recoverable braking energy or with a total applied braking energy during a braking operation. Brief description of the invention

[0010] One object of the present invention is to propose a method for determining energy consumption during vehicle operation. This object is achieved by a method according to claim 1.

[0011] The present invention relates to a method for determining a measure of energy use during operation of a vehicle having a first energy source for generating a first driving force to propel it in a first direction of travel, and at least one first actuatable braking system for applying a first braking force acting against the movement of the vehicle in the first direction of travel. For a period in which the demand for driving force from the first energy source is interrupted, the method comprises the following: - estimating the energy consumption during operation of the vehicle without requesting braking force from the first braking system, and - Using the estimated energy consumption during operation of the vehicle without requesting braking force from the first braking system as a basis for determining a measure of energy use during operation of the vehicle.

[0012] As previously mentioned, it is very important for overall economic efficiency that drivers drive vehicles economically, as fuel consumption is strongly influenced by their ability to utilize the energy stored on board. It is generally desirable to keep fuel consumption as low as possible, as the greater the amount of energy consumed, the more fuel is required to power the vehicle via the engine.

[0013] One way to determine a measure of energy use to assess energy use during vehicle operation is to determine the amount of fuel consumed over a given distance. However, this ignores important factors that can significantly affect the vehicle's fuel consumption. For example, it can be difficult to determine how much fuel consumption is due to reckless driving and how much is due to other factors that may be poorly controlled by the driver, e.g., flat versus hilly countryside, a heavily loaded vehicle, and / or a highway versus an urban environment with heavy traffic.

[0014] During operation of a vehicle, it may also be difficult for the driver to determine how well the energy fed into the storage when the vehicle is moving is actually being used, i.e. whether he / she is actually driving the vehicle economically.

[0015] The present invention provides the advantage of enabling an assessment of how a driver drives the vehicle in such a way that any influence of load or environment on the assessment is largely eliminated. This is achieved by determining how the vehicle is driven by the driver when the drive force demand is interrupted.

[0016] According to the invention, a representation of the fuel consumption is estimated when the vehicle is driven without actively applying braking force, i.e. with no braking force from the vehicle except that which the driveline transmits to the drive wheels when the driver interrupts the request for driving force, for example by releasing an accelerator pedal. The representation of the fuel consumption is therefore estimated in situations in which the request for driving force to propel the vehicle in the direction of travel is interrupted, i.e. situations in which the forward movement of the vehicle is due to the energy stored therein and is influenced by forces resulting from air resistance, rolling resistance and the braking force of the driveline in the form of internal friction (not when an internal combustion engine is disconnected), transmission friction and a force exerted by additional equipment.The vehicle is therefore not subjected to a braking system force that is actively applied via a braking system that can be actuated by the driver with a controllable, adjustable braking process, as is usually the case with (selectively) actuated braking systems.

[0017] The term coasting is defined here as a situation that, when the vehicle is moving, is represented by the situation that occurs when the driver interrupts the demand for propulsion, e.g., by releasing the accelerator pedal. In other words, the demand for propulsion is interrupted, and no further braking force is actively applied by the driver.

[0018] It should be appreciated that this situation may still involve some braking force acting against the vehicle, e.g., when the driveline is engaged and a gear is engaged, resulting in some engine braking. Equally, it may happen, e.g., in hybrid vehicles, that the control system decouples the internal combustion engine and, due to engine losses, the engine braking force is replaced, for example, by an appropriate regenerative braking force. Alternatively, or additionally, a braking force of a different magnitude may also be applied by the control system if deemed appropriate. However, this application of braking force still occurs without active driver request.

[0019] Based on the aforementioned fuel consumption representation, it is then possible to determine a measure of energy utilization and assess how the driver has used available energy while operating the vehicle. The higher the amount of energy consumed when the vehicle is allowed to coast, i.e., without the driver actively engaging any braking system, the more efficiently the driver drives the vehicle, as the stored energy is fully utilized. Conversely, the more braking force is actively requested via any braking system, the less energy-efficient the vehicle is driven.

[0020] According to the invention, the energy consumption during coasting is compared with the energy consumption via an active demand for braking force from one or more braking systems which are independent of the internal combustion engine, which means that they can be controllably actuated regardless of how the engine is controlled, e.g. regardless of whether it is decoupled from the rest of the drive train or not, for example a service braking system or an auxiliary braking system, in which case the comparison of the energy consumption between the different driving modes of the vehicle can be used to determine a measure of energy use for assessing the driving style of the vehicle by the driver.

[0021] In one embodiment, the vehicle is a hybrid vehicle with means for regenerative braking. In this case, a portion of the braked energy can be recovered and can be taken into account in the measure of energy use insofar as the braking force requested via regenerative braking is more economical than if, for example, a service braking system or a conventional, e.g. hydraulic, retarder braking system without brake force recovery is used, since a portion of the recovered braking energy can be stored in an energy storage device for further use in the form of electrical energy. However, due to the losses of the regenerative braking system, regenerative braking always results in significantly less energy being saved than coasting without any active application of braking force.The vehicle may also be equipped with both regenerative and non-regenerative braking systems, in which case the measure of energy use in the driver's assessment becomes smaller with an increasingly larger proportion of energy being braked via a non-regenerative braking system.

[0022] The measure of energy use determined during vehicle operation may be presented to the driver, for example, via a display in the form of, for example, an indication of a proportion, e.g., a percentage, of the assessment considered to represent the most economical driving style of the vehicle, which is normally achieved by simply rolling forward without actively applying braking force. The driver may receive information about assessments made, preferably continuously or at a desired time.

[0023] The energy usage measure can also be designed to be sent to a remote location, e.g., a fleet dispatch center, allowing two or more vehicles / drivers to be assessed centrally. The assessment presentation can also be combined with providing the driver with energy usage advice for improvement. An example of such an advice could be to interrupt the demand for braking force earlier, allowing the vehicle to coast without significant application of a braking system. Another example could be a recommendation to brake more carefully.

[0024] The method may include determining the energy utilization measure for one interruption of motive power after another, allowing the driver to obtain a rating for a particular interruption and thus obtain and display a new rating for each interruption. The energy utilization measure may also be determined continuously during a sustained interruption of motive power, in which case the measure / rating may change instantly depending on the driver's behavior during the interruption, e.g., whether they engage a braking system after a certain period of time.

[0025] The measure of energy use may also be in the form of a cumulative measure covering several consecutive interruptions of motive power, e.g. a cumulative measure of energy use from the time the vehicle is first put into operation by the driver, or a measure of energy use during the current trip or another suitable period, e.g. the current month.

[0026] The estimation of fuel consumption when the request for motive power is interrupted preferably starts as soon as it is interrupted, provided the vehicle is moving, with the aim of continuing for the period when the request is interrupted and, where appropriate, summing with previous estimates as previously indicated.

[0027] Further features of the present invention and advantages thereof are set forth in the following detailed description of embodiments and the accompanying drawings. Short description of the drawings Fig. 1a shows a drive train in a vehicle in which the present invention can be advantageously applied. Fig. Figure 1b shows an example of a control unit in a vehicle control system. Fig. Figure 2 shows an example of a method according to the present invention. Fig. Figure 3 shows an example of a representation of a measure of energy use for the driver of a vehicle. Fig. 4A to 4E show another example of a representation of a measure of energy use for the driver of a vehicle. Detailed description of preferred embodiments

[0028] In this description and the appended claims, a request for propulsion means a request for a positive propulsion force in the direction of travel of the vehicle. Interruption of the request for propulsion therefore means that there is no longer a request for a positive propulsion force in the direction of travel of the vehicle.

[0029] The present invention will now be exemplified with reference to a hybrid vehicle, but is equally applicable to other vehicles, e.g. electric vehicles, as well as to conventional vehicles powered solely by internal combustion engines.

[0030] Fig. Figure 1A shows a simplified general layout of a powertrain in a hybrid vehicle 100 according to an embodiment of the present invention. There are various types of hybrid vehicles, and the vehicle depicted here is a parallel hybrid vehicle.

[0031] This simplifies Fig. The vehicle 100 shown in Figure 1A has only one axle with drive wheels 113, 114, although the invention is also applicable to vehicles having more than one axle provided with drive wheels, as well as to vehicles having one or more further axles, e.g. one or more trailing axles.

[0032] The drive train of the parallel hybrid vehicle in Fig. 1A includes an internal combustion engine 101 connected in a conventional manner, via an output shaft of the engine 101, usually via a flywheel 102, to a transmission 103 via a clutch 106. The engine 101 is controlled by the vehicle control system via a control unit 115. Also controlled are the transmission 103 and the clutch 106, which in the present example is automatically operated by the vehicle control system, but could alternatively be manually operated by the vehicle control system via a control unit 116.

[0033] Transmissions in heavy-duty vehicles often take the form of a "manual" transmission 103, as in the illustrated embodiment, which is automatically actuated (by means of the vehicle control system), whereby the clutch 106 selectively connects the output shaft 102 of the engine 101 to the transmission 103.

[0034] The vehicle further comprises drive shafts 104, 105 connected to the drive wheels 113, 114 and which, as in a conventional internal combustion engine system, are driven by an output shaft 107 of the transmission via a final gear, e.g. a conventional differential 108.

[0035] In contrast to a conventional vehicle, the Fig. 1A also depicts an electric machine 110 connected to the input shaft 109 of the transmission 103 behind the clutch 106, meaning that the transmission input shaft 109 can be driven by the electric machine 110 even when the clutch 106 is open. The parallel hybrid vehicle can thus apply power to the drive wheels 113, 114 from two separate power sources simultaneously, i.e., both from the internal combustion engine 101 and from the electric machine 110. Alternatively, the vehicle can be driven by only one power source at a time, i.e., either from the internal combustion engine 101 or from the electric machine 110. The present invention is also applicable to other types of hybrid vehicles. The vehicle can also be provided with two or more electric machines, in which case an electric machine can be mounted adjacent to each drive wheel.

[0036] For example, the vehicle may be designed to have a conventional automatic transmission, with the electric machine being arranged before or after it.

[0037] The hybrid system also includes other components. Fig. 1A shows only the electric machine 110, an energy storage device 111, and a hybrid control unit 112, which is responsible, among other things, for the functions of the electric machine 110 and the energy storage device 111. The electric machine is provided with a variable-frequency power supply so that it can rotate a shaft at any desired speed and torque within the speed / torque range of the electric machine. In the example shown, the electric machine 110 is supplied with power from the energy storage device 111 via a power electronics unit 210 that generates the supply frequency. The energy storage device 111 can be arranged to be charged by regenerative braking by means of the electric machine 110 and the power electronics unit 210, but also by other means such as connection to an external energy source, e.g., a conventional power grid.

[0038] The electric machine 110 can thus be used to drive the vehicle 100 at, in principle, any desired speed by means of frequency control and to apply, in principle, any desired braking force up to the braking force corresponding to the maximum torque that the electric machine can transmit.

[0039] According to the present invention, a measure of energy use is determined in order to assess the driver's driving style of the vehicle in a certain type of situation, namely those in which the demand for driving power is interrupted and the vehicle's energy stored over several such interruptions is normally consumed at least partly by active braking by means of a braking system or simply by the other forces acting against the forward motion of the vehicle when, for example, it is coasting by means of the kinetic energy stored therein, without any vehicle-related braking force except for the powertrain losses, possibly by braking force applied by the vehicle control system, as previously discussed, without active demand from the driver, as well as by external forces acting on the vehicle's drive wheels, i.e.without any braking force actively requested via any of its braking systems.

[0040] With regard to the active demand for braking force from vehicle braking systems, the vehicle 100 further comprises various braking systems such as a conventional service braking system and a retarder braking system 117. Retarder braking systems such as the retarder braking system 117 may, for example, be located on the output shaft of the transmission 103, i.e., at the rear edge of the transmission, with the braking effect in this case being provided, for example, by electrical, hydraulic, or magnetic braking of the transmission output shaft and thus also of the drive wheels 113, 114 of the vehicle. The vehicle may also have further auxiliary braking systems such as an exhaust braking system, controllably adjustable engine braking system, compression braking system, and / or electromagnetic braking system, etc.

[0041] In the illustrated example of the vehicle control system, the service braking system, such as the retarder braking system 117, is actuated by means of a brake control unit 119, which transmits signals in a conventional manner, for example, to the controller(s) that regulate the requested braking force in braking systems. In the illustrated example, the brake control unit 119 also at least partially controls the regenerative braking by the electric machine. Based on commands initiated by the vehicle driver or other control units, the control unit 119 sends control signals to appropriate system modules to request the desired braking force. The driver may, for example, request retarder braking force or service braking force; however, if the control system determines that the desired braking force can be provided by more economical regenerative braking, the latter is used in practice.

[0042] As previously discussed, the functions of the vehicle components depicted are controlled by multiple control units. Control systems in modern vehicles generally include a communication bus system consisting of one or more communication buses for connecting multiple electronic control units (ECUs), or controllers, to various components in the vehicle. Such a control system may include a large number of control units, and responsibility for a particular task may be shared between two or more of them.

[0043] For simplicity, Fig. 1A only the control units 112, 115, 116, 118 and 119 are shown, however, vehicles 100 of the type shown are often equipped with considerably more control units, as the person skilled in the art will be aware.

[0044] In addition to the previously mentioned control units, Fig. 1A also includes a control unit 118 that controls the display of data on the instruments provided in the cab, which often include not only conventional gauges but also one or more displays. The control unit 118 enables the display of a measure representing the driver's energy usage on these one or more displays or on a display specifically designed for this purpose for the driver to see.

[0045] The invention may be embodied in any suitable control unit, and in the illustrated example, it is embodied in control unit 118. The calculations performed by control unit 118 (or the one or more control units in which the present invention is embodied) in estimating the driver's ability to use the energy stored in the vehicle in accordance with the present invention are likely to depend on signals received from the one or more control units controlling engine / electric motor functions, in the present example, control unit 115, and likely also on signals from control units 112, 119 and other control units (not shown) with which the vehicle is equipped, and / or on information from, for example, various sensors located in the vehicle.It is generally true that control units of the type considered here are normally designed to receive sensor signals from various parts of the vehicle.

[0046] Control units of the type considered here are also typically designed to provide control signals to various parts and components of the vehicle. For example, control unit 118 can provide signals to the displays for displaying data.

[0047] The control is often dependent on programmed instructions, usually in the form of a computer program, which, when executed in a computer or control unit, causes the computer / control unit to effect desired forms of control action, e.g., method steps according to the present invention. The computer program usually forms part of a computer program product comprising a suitable storage medium 121 (see Fig. 1B) on which the computer program is stored. The storage medium 121 may, for example, be a ROM (read-only memory), PROM (programmable read-only memory), EPROM (erasable PROM), flash memory, EEPROM (electrically erasable PROM), or a hard disk unit, etc., and may be located in the control unit or in a data transmission connection therewith, in which case the computer program is executed by the control unit. The vehicle behavior in a particular situation can thus be changed by modifying the computer program instructions.

[0048] An example of a control unit (control unit 118) which is simplified into Fig. 1B, may itself comprise a computing unit 120 in the form of, for example, any suitable type of processor or microcomputer, e.g., a digital signal processing circuit (digital signal processor, DSP) or a circuit with a predetermined specific function (application-specific integrated circuit, ASIC). The computing unit 120 is connected to a memory unit 121, which provides it, for example, with the stored program code and / or the stored data required by the computing unit to enable it to perform calculations. The computing unit 120 is also arranged to store partial or final results of calculations in the memory unit 121.

[0049] The control unit 118 is further provided with corresponding devices 122, 123, 124, 125 for receiving and transmitting input and output signals. These signals may comprise waveforms, pulses, or other features that the input signal receiving devices 122, 125 can recognize as information for processing by the calculation unit 120. The output signal transmitting devices 123, 124 are arranged to convert calculation results from the calculation unit 120 into output signals for transmission to other parts of the vehicle control system and / or the component or components for which the signals are intended. Each of the connections to the corresponding devices for receiving and transmitting input and output signals may be a cable, a data bus, e.g.a CAN bus (Controller Area Network), a MOST bus (Media Oriented Systems Transport) or another bus design, and / or a wireless connection.

[0050] Fig. 2 shows an example of a method 200 according to the present invention. The method begins at step 201 by determining whether the vehicle driver's request for motive power is discontinued. This may be indicated, for example, by the driver lifting their foot off an accelerator pedal or otherwise indicating to the vehicle control system that motive power capable of being transmitted to the drive wheels by the internal combustion engine 101 and / or the electric machine 110 is no longer desired to propel the vehicle.

[0051] The object of the present invention is to determine the way in which the vehicle is driven by the driver from the point of view of energy consumption, i.e. how the stored energy is used in practice by him / her during the period when the demand for driving power is interrupted, by determining a measure of energy use during the operation of the vehicle.

[0052] Thus, if it is determined in step 201 that the driver discontinues the request for motive power, the method proceeds to step 202 to determine whether braking power is actively requested from any of the vehicle's braking systems, i.e., whether braking power has been actively requested by the driver applying any braking system. As previously mentioned, regenerative braking is also considered one of the vehicle's braking systems. However, regenerative braking power is not normally explicitly selected by the driver, who actually requests application of any suitable braking system, whereupon the vehicle control system utilizes regenerative braking instead of requested braking whenever possible.As previously discussed, the braking effect of engine and other powertrain losses is passive and applies when the demand for motive power is interrupted, even without the driver actively requesting braking force, and therefore this braking effect does not represent an active demand for braking force from a braking system.

[0053] If braking force is actively requested by the driver of the vehicle, the method proceeds to step 208 described below, whereas if no braking force is requested, it proceeds to step 203 and an estimate is made of how the stored vehicle energy is consumed when coasting, ie, without requesting driving force and without actuating a braking system. This energy consumption E u can be a function of time and can be estimated, for example, as given below.

[0054] When the vehicle is moving but no internal braking systems are applied, the energy stored in them is consumed mainly by braking forces caused by air resistance, rolling resistance and powertrain losses, especially friction in the internal combustion engine.

[0055] When the vehicle is traveling on a perfectly flat road, the decrease in stored energy can be estimated as mv122−mv222, i.e. the difference in kinetic energy, where v1 is the vehicle speed when the demand for motive power is interrupted and v2 is the vehicle speed when the demand for motive power is again. In one embodiment, this formula can be used in estimating the amount of stored energy consumed when the demand for motive power is interrupted and no braking force is actively requested. However, this approach does not take into account changes in vehicle speed caused, for example, by inclined driving surfaces. In one embodiment, therefore, an estimation is made which includes more / different factors in the calculation. When estimating energy consumption when the demand for motive power is interrupted, for example, the following factors can be used.

[0056] One cause of energy consumption during vehicle operation is air resistance, which can be determined as the air resistance force F = ½ρACdv 2where ρ = density of air, A = cross-sectional area of the vehicle in the direction of travel, v = relative speed of the vehicle against the wind. The air resistance is therefore strongly (quadratically) dependent on the vehicle speed. Cd = drag coefficient, which depends on the design of the vehicle surfaces exposed to the wind and is in principle influenced by all external vehicle parts. Calculating the drag coefficient can be difficult, but the air resistance force can be estimated, for example, by the vehicle control system by subtracting the other opposing forces discussed below from the power developed by the combustion engine / electric motor, which is available, for example, via the combustion engine control unit. The drag coefficient can therefore also be estimated. Alternatively, Cd can be measured, but will change if, for example, another trailer is attached.The air resistance can therefore be calculated by the vehicle control system.

[0057] The rolling resistance of the vehicle can be expressed as F = CrN, where Cr is the rolling resistance coefficient, which depends mainly on the vehicle's tires / wheels, the road surface, and the normal force N. The actual vehicle weight is of great importance. The rolling resistance force can also be determined by the vehicle control system.

[0058] Another factor is the powertrain losses, which vary in nature. The internal friction power of the internal combustion engine can be calculated as P=Mω, where M is the drag torque specific to the engine, ω is the angular velocity (2n*the engine speed), and the energy consumed can thus be obtained by integrating this power over time. It can be seen that the friction power depends on the speed and increases with increasing speed. If the vehicle is driven while the internal combustion engine is decoupled from the drive wheels, this term can be deleted.

[0059] A good estimate of the energy consumed during coasting can usually be obtained based on the factors mentioned so far. If an even more accurate estimate is desired, the calculation can include other factors such as gearbox friction, which also depends on speed. Losses due to gearbox efficiency may also apply, as may friction losses in axles / hubs, which again depend on speed. Efficiency also plays a role here. The combined losses of the driveline, or the individual losses of its various components, can be stored in the control system for various speeds and used in making estimates according to the invention.

[0060] In step 203, the energy consumption that occurs when the vehicle is coasting can thus be estimated by summarizing the energy consumption across the parameters. The method can then be designed to remain at step 203 via a step 204 as long as the condition is met, i.e., as long as the vehicle driver does not request either drive or braking force.

[0061] If it is determined in step 204 that the condition for the estimation according to step 203 is no longer met, either because driving force is requested again or because braking force is actively requested, the method proceeds to step 205 to store the estimated energy consumption E uThe energy consumption estimated in step 203 may be stored as a cumulative value over the period in which the vehicle was explicitly driven without any request for propulsion or braking force, and / or summed together with estimated energy consumptions over previous periods when the conditions for step 203 were met. The method thus estimates how much of the vehicle's stored energy is converted into other forms of energy as it rolls along a road without any influences other than external factors and internal losses.

[0062] The method then proceeds to step 206 to determine whether the condition for step 203 is no longer met because motive power is still being requested. If so, the method proceeds to step 207, described below. If it is determined in step 206 that motive power is still not being requested, but the condition for step 203 is not met for another reason, e.g., because an internal braking system of the vehicle has been applied, the method returns to step 202 before proceeding to step 208.

[0063] In step 208, it is determined whether a regenerative braking system has been applied, ie, whether the vehicle 100 is being braked by the electric machine 110. Regenerative braking is normally not explicitly requested by the driver, but is activated by the vehicle control system rather than, for example, applying the braking system requested by the driver, e.g., wheel brakes or retarder brakes.

[0064] If the vehicle is subjected to regenerative braking, the method proceeds from step 208 to step 209 to determine energy consumed by regenerative braking. This estimate may be configured to determine the amount of energy converted through the use of regenerative braking, which may be determined by any suitable means, e.g., by determining the braking force applied by the electric machine 110. This force can usually be determined with good accuracy. Step 209 may also be configured to estimate the amount of energy actually fed into the energy storage device during regenerative braking if it differs from the braking force applied by the electric machine.For example, it's possible to apply a larger force, with only a portion of the recovered energy being fed into the energy storage system, while a portion is converted into heat or used in another way. Typically, however, the electric machine applies a braking force that essentially yields electrical energy that can be absorbed by the energy storage system. A person skilled in the art will recognize that losses also occur in regenerative braking systems, meaning that the applied braking force is greater than the energy actually fed into the energy storage system.

[0065] In one embodiment, the amount of energy actually recovered by feeding into the energy storage is estimated, and any losses during regenerative braking are absorbed braking energy minus energy fed into the storage. However, for driver assessment purposes, as indicated below, it may be advantageous not to perform such an accurate determination of the amount of energy actually fed into the storage, but instead to estimate the energy consumption during regenerative braking as the energy that can be stored when regenerative braking is at its full capacity. In one embodiment, therefore, the amount of energy that could theoretically have been recovered at full capacity is estimated, regardless of the amount actually recovered during braking.

[0066] It will be appreciated that the braking force applied by the regenerative braking system may be less than the total braking force requested, in which case further non-regenerative braking force may be applied, e.g. using the vehicle's service braking system or an additional braking system. In step 210, it is therefore determined whether regenerative braking accounts for the total braking force applied. As long as this is the case, the method proceeds to step 211 to determine whether the braked force should be further estimated, ie whether the request for motive power is still interrupted and braking force is requested. If this is the case, the method returns to step 208 and further estimated.If it is determined in step 211 that the braked force is not to be estimated further, the method proceeds to step 212 for data storage as in step 205 previously, before proceeding to step 206 for determining whether brake force is requested or not requested, as previously indicated.

[0067] If it is determined in step 210 that not only regenerative braking is taking place, but additional braking is also taking place, the energy consumption via this additional braking force is estimated in step 213. The method also proceeds directly from step 208 to step 213 if regenerative braking is not taking place. The energy consumption for additional braking forces can be estimated, for example, as the difference between the total braking force applied and the braking force applied via the regenerative braking system. Alternatively, the braking force can be estimated specifically for the specific braking system in use.

[0068] The braking force generated by the retarder depends on its position, e.g. behind the gearbox as in Fig. 1A. The retarder brake power can be determined, for example, by multiplying the torque generated by the retarder and acting on the transmission output shaft by the angular velocity of the output shaft. In this case, the dissipated energy can be obtained, as before, by integrating this power over time. The retarder braking torque at that time is usually available via the vehicle control system.

[0069] In disc brake systems and drum brake systems, brake pressures (from which braking torques can be calculated based on physical relationships known to those skilled in the art) are often available via the control system, or the braking torque is directly available. This allows the control unit 118 to be easily supplied with the desired information. It is known that the energy E can then be expressed as E=Fs, where F represents the force and s represents the distance, which is the same as the time integration of velocity as a scalar and velocity as a vector, i.e., the power P = F (force acting on vehicle) * v (vehicle speed).

[0070] There are numerous different ways to determine braking forces for disc and drum brakes. For example, the torque of these brakes can be multiplied by the angular velocity of the wheels, in which case this power can be integrated over time as previously stated to obtain the braking energy. If no information about this braking torque is available, a model can be used to derive the braking torque from the brake pressure. This information is usually all known from the vehicle data and / or is available via the control system. The braking force for disc and drum brakes can also be determined as F=ωmv where M is the braking torque, v is the vehicle speed, and ω is the angular velocity, allowing power / energy to be calculated as previously stated. Braking energy can thus be determined in a suitable manner.

[0071] It should also be noted that the calculations exemplified above are merely examples of how braking energy can be determined. Vehicle control systems are continually evolving and becoming increasingly better equipped to calculate braking energy via vehicle braking systems, and the scope of the present invention includes performing the calculations in the manner most appropriate for the particular vehicle.

[0072] Applied braking forces are thus estimated and summarized as before until braking force is no longer requested or driving force is requested again, whereupon the method proceeds to step 207 and the result is presented to the driver of the vehicle.

[0073] In step 207, the result is presented to the driver. This can be done in a variety of ways. For example, it is possible for data to be shown on a display with a measure of energy use that represents both an assessment of the last period when the demand for drive power was interrupted and an overall assessment of the entire journey of the vehicle. This data can, for example, be shown on a screen only during the time when the demand for drive power is interrupted, or alternatively, for example, can be shown continuously. The data can, for example, also be designed to be accessible via screen displays that are viewed by the driver of the vehicle. Data such as that mentioned above can, alternatively or additionally, be presented to the driver in other suitable ways.They can, for example, be presented visually in another suitable manner, or via suitable acoustic / voice signals or via suitable haptic signals. The method then ends at step 214.

[0074] Fig. Figure 3 shows an example of what the display might look like for the driver of the vehicle. Reference numeral 301 denotes immediate feedback on the driver's behavior, as described in more detail in Fig. 4A to 4E. This feedback shows in the form of a bar chart a value to the right or left of a reference line 401 (see Fig. 4A) can assume how well he / she uses the vehicle's stored energy in a situation where the demand for motive power is interrupted. Fig. 4A to E represent different situations and the bar represents a different degree of economical driving, so that a completely filled bar (indicated by hatching, see Fig. 4B) on the left side of the reference line 401 represents the maximum use of the vehicle's stored energy, while a bar taking a value on the right side of the reference line (also indicated by hatching, see Fig. 4E) represents the desired behavior during vehicle operation. Reference line 401 indicates maximum recovery through regenerative braking.

[0075] If the vehicle is driving with active demand for drive power, e.g. via an accelerator pedal, the bar is inactive, Fig. 4A. When the drive force request is subsequently interrupted, the bar assumes different positions depending on the driver's behavior. Fig. Figure 4B illustrates a situation in which neither propulsion nor braking force is requested, i.e., the vehicle is coasting. As previously stated, this represents the most economical driving mode for the vehicle, as no energy is wasted unnecessarily. Therefore, a fully filled bar is shown to the left of the reference line.

[0076] However, as soon as the driver applies braking force, energy is lost, even if regenerative braking force is applied, because the energy conversion in the regenerative braking system is not lossless.

[0077] Fig. 4C and Fig. 4D each represent situations with a different degree of application of a moderate braking force, whereby a lower application of braking force allows a higher proportion of the braking energy to be recovered, so that the bar in Fig. 4C shows a better use of energy than when applying stronger braking force in Fig. 4D, which represents the maximum braking force that can be applied through regenerative braking. Fig. 4E represents heavy braking, resulting in a very large proportion of the braked energy being lost, as the braking force far exceeds the force that can be recovered through regenerative braking (reference line 401 thus indicates the limit for maximum regenerative braking force recovery). In this case, the bar therefore moves in the opposite direction, indicating a very uneconomical / undesirable use of the vehicle's stored energy.

[0078] The bar can therefore change instantly when the driver changes the braking force requirement. In addition to providing immediate feedback on the use of vehicle energy, Fig. 3 a composite estimated measure 302 for the specific period with intermittent demand for driving power, ie during a sustained interruption of driving power, or a cumulative measure for the vehicle's travel or another suitable period. Different measures relating to different periods can also be displayed. The exemplary screen display in Fig. 3 also shows the charge state 303 of the energy storage device.

[0079] As can be seen, the example bar chart can be Fig. 3 to 4 can be shaped in very different ways, e.g. vertical, mirror-image, in the form of an indicator, etc., as long as the difference between the situation in which braking force is actively requested and the situation in which it is not requested is clear.

[0080] The Fig. The values illustrated in Figures 3 to 4 can be calculated, for example, using the following non-limiting algorithm, for example as a percentage measure: reco=Xeco(n0)−Xeco(nreset)Xtot(n0)−Xtot(nreset)×100 (%) where r eco the measure of how well the driver uses the vehicle's stored energy, expressed as a percentage. X eco is a composite value for the energy used, ie the proportion of X tot which does not lead to braking losses during interruptions in the drive power. X tot is a composite value representing the total amount of energy consumed during interruptions in the driving force. n0 is an index for the last determined cumulative value. n reset is an index for the respective value at the last reset.

[0081] The algorithm in the hybrid system for calculating Xeco and X tot can be written as Xeco=∫necomin(−mv(v˙+g sin(α)),Psat)θdtXtot=∫−mv(v˙+g sin(α))θdt where n eco is a factor describing the combined efficiency when driving without a request for motive power and depends on whether regenerative braking and / or non-regenerative braking is requested; m is the estimated weight of the vehicle; v is the vehicle speed; V̇ is the vehicle acceleration; g is the gravitational constant (9.82 m / s 2 ); a is the gradient of the road; P satis a saturation level for the sum of driving resistance and regenerative braking, i.e., the total braking force that can be obtained based on these two factors. In one embodiment, the theoretically maximum possible energy recovery via regenerative braking is used in this determination, as indicated below. θ is a factor that equals one when the driver's drive force demand is less than or equal to zero. If the drive force demand is positive, this factor is zero.

[0082] n eco and P sat can be used, for example, with the algorithm ηeco=Ps+ηgPgPs+PgPsat=Ps+Pgsat be calculated at which n g is the overall efficiency for regenerative braking; P s is the estimated driving resistance, defined as air resistance + rolling resistance + internal losses in the vehicle's drivetrain; Pg the current braking level P brake up to P g sat and as min (P brake , P g sat ) can be expressed; P g sat is the saturation efficiency during regenerative braking.

[0083] If the demand for driving force is interrupted at a time when no braking systems are applied, η eco 1 (P g =0). This is the best way to utilize the vehicle's stored kinetic energy. The energy lost by storing energy in the hybrid system's energy storage is determined by the factor η g described. If the hybrid system had no losses, ie if η g= 1, the efficiency during braking by the hybrid system would be the same as if the vehicle were driven without applying any braking force when the demand for motive power is interrupted. The portion of X not covered by the above tot represents pure energy loss.

[0084] A simple procedure for obtaining a good measure of the driver's driving style is thus possible, in that the example shown produces an average assessment since the last reset. The driver may preferentially reset the assessment so that, for example, he or she can receive immediate feedback on how the vehicle reacts to changes in driving style. However, his or her control system can still store the measure for the entire trip and, for example, even earlier data. Reference points for calculations at reset points can therefore be determined, e.g., X eco(n reset ) and X tot (n reset ), as stated previously. A measure may also be provided immediately after each situation, starting when the driver interrupts the request for motive power and continuing until he / she requests motive power again, i.e., a measure for each period when θ is equal to one, as stated previously.

[0085] Calculated parameters can, for example, be sent to a transport management system for managing the vehicle fleet to which the vehicle belongs, e.g. Scania Fleet Management from Scania, which allows the vehicle owner to review assessments of different drivers.

[0086] As previously mentioned, in one embodiment, the energy actually recovered through regenerative braking is not determined, but rather the energy that would be recovered if the regenerative braking system were operating optimally. For example, various circumstances may cause the efficiency of regenerative braking to become low, e.g., because the energy storage device is full, or the prevailing ambient temperatures are such that it cannot absorb as much energy as under optimal conditions, or because regenerative braking is not operating optimally for some other reason.

[0087] If the driver's assessment of the vehicle's performance under such conditions is negative, even though they have essentially driven the vehicle economically, simply because the hybrid system is not operating optimally, this could lead to them continuing to drive reluctantly in a fundamentally desirable manner, resulting in reduced savings. In such situations, it may therefore be beneficial to determine an assessment of vehicle operation that assumes that the theoretically maximum brake force recovery has occurred under the prevailing conditions, with the driver's assessment based on driving with an optimally operating system, rather than on deficiencies or other limiting factors.

[0088] The Fig.The method illustrated in Figure 2 may also be designed to be applied only while the vehicle's cruise control functions are inactive, since the vehicle control system is largely responsible for the vehicle's driving behavior when a cruise control function is active. However, regardless of whether a cruise control function is active or not, the present invention is applicable as soon as the driver actively interrupts the request for driving power.

[0089] The invention is described above with reference to a parallel hybrid system, but is also applicable to vehicles with other types of hybrid systems, such as electric vehicles that have only one or more electric motors. The invention is also applicable to conventional vehicles with exclusively internal combustion engine operation, in which case the above section on regenerative braking and energy storage does not apply.

Claims

[1] Method for determining a measure of energy use during operation of a vehicle (100), - which is equipped with a first energy source (101) for generating a first driving force for driving the vehicle (100) in a first direction of travel and with at least one first braking system, - which can be actuated to apply a first braking force acting against the movement of the vehicle (100) in the first direction of travel, and - which has an energy source for generating regenerative braking force acting on at least one wheel of the vehicle (100), wherein for a first period of time in which the request for motive power from the first energy source is interrupted, the method comprises: - estimating the energy consumption during operation of the vehicle (100) without requesting braking force from the first braking system, and - using the estimated energy consumption during operation of the vehicle (100) without requesting braking force from the first braking system as a basis for determining a measure of energy use during operation of the vehicle (100), characterized by , that the procedure further comprises: - Compare energy consumption during operation without a demand for braking force from the first braking system and then when the demand for driving force from the first energy source is interrupted, with the energy consumption during regenerative braking; - using the comparison as a basis for determining a measure of the energy use of stored energy of the vehicle (100) during operation of the vehicle (100) for presenting this measure to the driver of the vehicle (100) via a display. [2] The method of claim 1, further comprising, for the first period of time, comparing energy consumption during operation without demand for braking force from the first braking system with energy consumption via active use of one or more systems of the at least one first braking system, and using the comparison as a basis for determining the measure of energy use during operation of the vehicle (100). [3] The method of claim 1, wherein the energy source for generating regenerative braking force acting on at least one wheel of the vehicle (100) is at least one electric machine (110). [4] The method of claim 1 or 3, further comprising taking into account the efficiency during regenerative braking in the comparison. [5] The method of any one of claims 1, 3 or 4, further comprising: - during the determination of the measure of energy use during operation of the vehicle (100), considering the operation of the vehicle without requesting braking force from the first braking system as a better use of energy during operation of the vehicle than the use of regenerative braking for its operation. [6] Method according to one of claims 1 or 3 to 5, wherein the vehicle (100) is provided not only with the energy source for generating regenerative braking force acting on at least one wheel of the vehicle (100), but also with at least one further braking system, further comprising comparing the energy consumption during operation without request for braking force from the first braking system, with the energy consumption during regenerative braking and with the energy consumption by actuating the at least one further braking system and using the comparison as a basis for determining the measure of energy use during operation of the vehicle (100). [7] Method according to one of claims 1 or 3 to 6, so that the vehicle (100) is provided not only with the energy source (110) for generating regenerative braking force acting on at least one wheel of the vehicle (100), but also with at least one further braking system, and so that during the determination of the measure of energy use, regenerative braking is considered to be the better use of energy than operation with demand for braking force from the at least one further braking system. [8] A method according to any one of claims 1 or 3 to 6, wherein, in estimating energy consumption by regenerative braking, a degree of maximum efficiency for regenerative braking is determined as the degree of maximum efficiency at which recovered energy can be stored at full capacity of the regenerative braking system. [9] A method according to any one of the preceding claims, further comprising determining the measure of energy use during operation of the vehicle (100) in the form of an indication of a proportion of a measure which is determined to correspond to a preferred driving style of the vehicle (100), which is the mode of operation without request for braking force from the first braking system. [10] A method according to any one of the preceding claims, wherein the determination of the measure of energy use takes place only when the request for driving force from the first energy source is interrupted. [11] A method according to any one of the preceding claims, wherein determining the measure of energy use takes the form of a measure for the entire first period. [12] A method according to any one of the preceding claims, wherein the measure of energy use is determined and aggregated over a plurality of successive periods in which the demand for driving power from the first energy source is interrupted. [13] A method according to any one of the preceding claims, further comprising continuously displaying changes in the first measure during the first period. [14] Method according to one of the preceding claims, in which the at least one first braking system is a service braking system, retarder braking system, exhaust braking system, controllably adjustable engine braking system, compression braking system, electromagnetic braking system and / or further additional braking systems. [15] Method according to one of the preceding claims, wherein the at least one first braking system is a braking system which is independent of an internal combustion engine. [16] Method according to claim 15, in which the at least one braking system can be controllably actuated regardless of whether the internal combustion engine is decoupled from the drive train behind it. [17] A method according to any one of the preceding claims, wherein a request for braking force from the first braking system is in the form of a request for braking force initiated by a driver of the vehicle. [18] A method according to any one of the preceding claims, wherein a driver of the vehicle interrupts the request for driving power from the first energy source. [19] Method according to one of the preceding claims, further comprising: - Estimate the energy consumption during the first period when the first braking force is not activated, - Estimate the total energy consumption during the first period, and - Determine the first measure of energy use as the ratio between the energy consumption when the first braking force is not activated and the total energy consumption. [20] A method according to claim 19, wherein the total energy consumption during the first period is in the form of the energy consumed when the first braking force is not activated and the energy consumed by the at least one of the first braking systems. [21] A computer program comprising program code which, when executed in a computer, causes the computer to apply the method according to any one of claims 1 to 21. [22] A computer program product comprising a computer-readable medium and a computer program according to claim 22, wherein the program is included in the computer-readable medium. [23] System for determining a measure of energy use during operation of a vehicle (100), - which is equipped with a first energy source (101) for generating a first driving force for driving the vehicle (100) in a first direction of travel and with at least one first braking system, - which can be actuated to apply a first braking force acting against the movement of the vehicle (100) in the first direction of travel, and - which has an energy source for generating regenerative braking force acting on at least one wheel of the vehicle (100), wherein for a first period of time during which the demand for motive power from the first energy source is interrupted, the system comprises: - means adapted to estimate the energy consumption during operation of the vehicle (100) without requesting braking force from the first braking system, and - means adapted to use the estimated energy consumption during operation without requesting braking force from the first braking system as a basis for determining a measure of energy use during operation of the vehicle (100), characterized by , that the system further includes: - Means designed to compare the following energy consumptions: the energy consumption during operation without a demand for braking force from the first braking system and when the demand for driving force from the first energy source is interrupted, with the energy consumption during regenerative braking; - means adapted to use the comparison as a basis for determining the measure of energy use of stored energy of the vehicle (100) during operation of the vehicle (100) for presenting this measure to the driver of the vehicle (100) via a display. [24] Vehicle, characterized by that it is equipped with a system according to claim 23.

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