Method of calculating a suggested speed range for a vehicle, corresponding system and computer program product

Abstract

A method (30) of calculating a suggested speed range (42) of a vehicle is described. The method comprises detecting (302) a maximum speed limit in effect on the section of road travelled by the vehicle, and setting (314) an upper limit (VH) of the suggested speed range (42) to a value lower than or equal to the detected maximum speed limit. The method further comprises detecting (308, 310, 312) one or more of the following parameters: i) energy conditions of a traction battery of the vehicle; ii) temperature of one or more cells of the traction battery of the vehicle; and iii) power absorbed by one or more auxiliary loads of the vehicle. The method also comprises setting (314) the upper limit (VH) and / or a lower limit (VL) of the suggested speed range (42) as a function of the detected parameters to increase the range of the vehicle.

Description

[0001] “Method of calculating a suggested speed range for a vehicle, corresponding system and computer program product” ****

[0002] TEXT OF THE DESCRIPTION

[0003] Fiel of the invention

[0004] The present invention relates to a method and a system for calculating and communicating to the driver of a vehicle a suggested speed range.

[0005] Prior art

[0006] Systems of the aforementioned type are known, for example, from document US 2010 / 0315218 A1 . Such a known system comprises a GPS receiver, an image recognition device, one or more sensors, one or more electronic processing units (processors), and a display on the vehicle dashboard. The GPS receiver and / or the image recognition device detect the legal speed limit in effect on the road the vehicle is travelling on. The sensors detect the environmental conditions surrounding the vehicle. The processor receives data from the GPS receiver and / or image recognition device, and receives data from sensors; calculates a maximum safe speed; and calculates a safe speed range as a function of the maximum safe speed and the legal speed limit. The dashboard display alerts the driver if the maximum safe speed is below the legal speed limit, and displays the safe speed range on a display speedometer if the maximum safe speed is below the legal speed limit.

[0007] In the known system described above, the parameters relating to consumption and range of the vehicle are not considered, which are of ever- increasing importance especially in hybrid and electric vehicles.

[0008] Object of the invention

[0009] The object of the present invention is to provide a method and a system for calculating and communicating to the driver of a vehicle a suggested speed range that improve the driving safety and the fuel consumption of the vehicle. Summary of the invention

[0010] In one aspect, the invention relates to a method, possibly implemented by an electronic unit (for example, a microprocessor or a vehicle control unit), of calculating a suggested speed range for a vehicle. The method comprises detecting a maximum speed limit in effect on the section of road travelled by the vehicle, and setting an upper limit of the suggested speed range to a value lower than or equal to the detected maximum speed limit. The method further comprises detecting one or more of the following parameters: i) energy conditions of a traction battery of the vehicle; ii) temperature of one or more cells of the traction battery of the vehicle; and iii) power absorbed by one or more auxiliary loads of the vehicle. The method comprises setting the upper limit and / or a lower limit of the suggested speed range as a function of the detected parameters to increase the range of the vehicle.

[0011] According to another aspect, the invention relates to a system for calculating a suggested speed range of a vehicle. The system comprises at least one sensor configured to detect a maximum speed limit in effect on the section of road travelled by the vehicle, and one or more sensors configured to detect one or more of the following parameters: i) energy conditions of a traction battery of the vehicle; ii) temperature of one or more cells of the traction battery of the vehicle; and iii) power absorbed by one or more auxiliary loads of the vehicle. The system further comprises an electronic control unit configured to operate according to the method of one or more embodiments.

[0012] According to another aspect, the invention relates to a corresponding computer program product that can be loaded into a memory of at least one processing device (for example, a microprocessor, an electronic control unit or a vehicle control unit) and comprising software code instructions to carry out the method when the program is executed by the at least one processing device. As used herein, a reference to such a computer program product is intended to be equivalent to a reference to a computer-readable medium that contains instructions for controlling the processing device for the purpose of coordinating the implementation of the method according to one or more embodiments. A reference to “at least one processing device” is intended to highlight the possibility that one or more embodiments are implemented in a modular and / or distributed form.

[0013] Detailed description of the invention

[0014] Further features and advantages of the invention will emerge from the following description with reference to the attached drawings, provided purely by way of non-limiting example, wherein:

[0015] - Figure 1 is a graph that illustrates different energy consumption curves of a vehicle (Energy Per Meter, EPM - expressed in kWh / km) as a function of the vehicle speed (\ / - expressed in km / h), in four different operating conditions of the vehicle;

[0016] - Figure 2 is a graph that illustrates different curves of the maximum safe speed of a vehicle ( VMAX - expressed in km / h) as a function of the grip coefficient ( - dimensionless) between the tires of the vehicle and the ground, in four different drive modes of the vehicle;

[0017] - Figure 3 illustrates a flowchart of a method according to one or more embodiments of the present description; and

[0018] - Figure 4 illustrates a vehicle speedometer according to one or more embodiments of the present invention.

[0019] As mentioned, one or more embodiments relate to a method of calculating and communicating a suggested speed range to the driver of a vehicle, as a function of the environmental conditions surrounding the vehicle (e.g., environmental inputs) and as a function of an energetic objective, i.e. , in order to increase the range of the vehicle.

[0020] In fact, the Inventors have noted that often the legal speed limit (i.e., the maximum speed imposed by the speed limit in effect on the section of road travelled by a vehicle) does not optimize the energy consumption of the vehicle. Therefore, the method according to the present invention calculates a suggested speed range as a function of various parameters detected by the vehicle, such as for example the legal speed limit (which represents an upper limit), the energy conditions of the vehicle, the grip conditions between the tires of the vehicle and the ground, and optionally other environmental conditions. Once the suggested speed range has been calculated, the method involves indicating (for example, visually on the speedometer displayed in the vehicle’s instrument panel) this suggested speed range, so that the driver can be informed about the speed range in which it is suggested to travel to maintain safe driving conditions and at the same time optimize vehicle consumption.

[0021] In the following of the present description, reference will be made mainly to an electric traction vehicle (Battery Electric Vehicle, BEV). Nonetheless, one or more embodiments can be applied in a similar way to hybrid vehicles (Hybrid Electric Vehicle, HEV) or vehicles having an internal combustion engine (ICE).

[0022] In order to better understand the invention, Figure 1 illustrates different curves of the energy consumption EPM of a vehicle (in kWh / km) as a function of the vehicle speed V (in km / h), under four different operating conditions of the vehicle, i.e., depending on the auxiliary loads (such as air conditioning, heated seats, etc.) active during travel. For example, in a first operating condition (continuous curve), the power absorbed by the auxiliary loads is equal to 0 kW, i.e., there are no active auxiliary loads and the only energy absorption from the batteries is that due to the electric motor for propulsion of the vehicle. In this first operating condition, consumption increases according to a monotonic curve as the speed of the vehicle increases, because friction increases as speed increases. In a second operating condition (dotted curve), the power absorbed by the auxiliary loads is equal to 0.5 kW, i.e., there are few active auxiliary loads (e.g., only one heated seat turned on). In a third operating condition (dash and dot curve), the power absorbed by the auxiliary loads is equal to 2 kW, i.e., there are more auxiliary loads active (e.g., all heated seats turned on). In a fourth operating condition (dashed curve), the power absorbed by the auxiliary loads is equal to 10 kW. In the second, third and fourth operating conditions (and in general, whenever there is an absorption of energy not used for the propulsion of the vehicle), the consumption curve tends to diverge towards infinity as speed approaches zero, since the consumption of the auxiliary loads remains constant over time and would lead to battery exhaustion even if the vehicle remains stationary. The consumption curve, however, tends to overlap with the curve of the first operating condition as the speed increases, since the consumption due to the auxiliary loads becomes increasingly negligible compared to friction. In the intermediate portion, the consumption curve therefore presents a minimum, which corresponds to a speed value that maximizes the range of the vehicle in that specific operating condition.

[0023] Again for the purpose of a better understanding of the invention, Figure 2 illustrates different curves of the maximum safe speed VMAX of a vehicle (in km / h) as a function of the grip coefficient fj (dimensionless) between the tires of the vehicle and the ground, in four different drive modes of the vehicle. In general, the maximum safety speed can be set to a higher value as the grip coefficient increases, but the correlation can vary depending on the drive mode of the vehicle: the choice depends on the driving style of the driver, making the grip target more or less stringent (in particular, greater slippage may be permitted in sportier drive modes). For example, Figure 2 illustrates an MR mode (“max range”, i.e., a range maximization mode - continuous curve), a GT mode (“Gran Turismo”, i.e., a “normal” drive mode, which is often the mode set by default when starting the vehicle - dotted curve), an SP mode (“sport”, i.e., a mode that allows performance more geared to sporty driving - dashed and dotted curve), and a CO mode (“racing”, i.e., a mode that allows maximum performance and greater slippages, for example by excluding the intervention of one or more vehicle safety controls such as ESP, TCS, etc. - dashed curve). For example, the range maximization mode MR limits the maximum speed to a value of 130 km / h regardless of the value of the grip coefficient.

[0024] The method according to the present invention, therefore, takes into account the maximum speed limit in effect on the section of road travelled by the vehicle, the detected energy conditions (e.g., absorption due to auxiliary loads), and the detected environmental conditions (e.g., the grip coefficient) to calculate a speed range in which the vehicle can be driven safely while maximizing the range. Once this speed range has been calculated, a corresponding indication is provided to the driver (e.g., visually on the speedometer of the vehicle).

[0025] Figure 3 illustrates a flowchart of a method 30 according to the present invention. After a start step 300, the method comprises a step 302 in which the vehicle detects the maximum speed limit in effect on the current section of road. For example, the maximum speed limit can be detected by recognizing the relevant road sign via a vehicle camera, and / or by satellite localization (GPS) and use of the navigation features of the vehicle. Optionally, and with the same modalities, in step 302 the vehicle can detect the minimum speed limit in effect on the current section of road (where provided, for example on some lanes of motorway sections). In step 304, the vehicle detects the drive mode currently used by the driver (e.g., MR, GT, SP, or CO). In step 306, the vehicle estimates the value of the grip coefficient For example, this estimate can be made as a function of one or more detected parameters (including environmental) by modifying a default value according to an algorithm that considers: wheel revolutions, longitudinal acceleration, transversal acceleration, supplied driving torque, presence and intensity of rainfall (which can be detected via a dedicated sensor, the same one that automatically activates the vehicle’s windshield wipers, or again based on GPS location). In step 308, the vehicle detects the instantaneous energy conditions of the high-voltage battery (i.e., the battery that provides the energy for the electric traction). These energy conditions may include the state of charge of the battery (SOC) and / or the state of health of the battery (SOH). In step 310, the vehicle detects the temperature (or temperatures, if equipped with multiple sensors) of the high voltage battery cells. Optionally, in step 310 the vehicle also detects possible voltage unbalances between the high voltage battery cells. In step 312, the vehicle detects the number and type of activated auxiliary loads (e.g., high voltage actuators such as the air conditioning compressor) and estimates the power absorbed by the active auxiliary loads. In step 314, the vehicle determines a suggested speed range as a function of the parameters detected in the previous steps, and in particular respecting one or more of the following conditions:

[0026] - the upper limit VH cannot be greater than the maximum speed limit detected at step 302;

[0027] - the lower limit VL cannot be less than the minimum speed limit detected at step 302;

[0028] - the upper limit VH and the lower limit VL are calculated as a function of the drive mode detected in step 304 (e.g., the speeds suggested in a more eco-friendly drive mode, such as MR mode, will be lower than the speeds suggested in a sportier drive mode like the SP mode);

[0029] - the upper limit VH is calculated as a function of the grip coefficient estimated at step 306 (e.g., the upper limit VH decreases as the grip coefficient decreases and / or in the presence of precipitation on the road); - the upper limit VH and the lower limit VL are calculated as a function of the energy conditions of the battery detected in step 308 (e.g. , the values of these limits will be lower if the state of charge, SOC, of the battery is lower: the suggested speed, for example, could be equal to 90 km / h when the charge percentage is 10%, and equal to 95 km / h when the charge percentage is 20%);

[0030] - the upper limit VH and the lower limit VL are calculated as a function of the temperatures of the battery cells detected at step 310 (e.g. , the suggested speed is lower the higher the temperature unbalance between the different battery cells: the suggested speed, for example, could be equal to 90 km / h when the temperature difference is 15°C, and equal to 95 km / h when the temperature difference is 10°C);

[0031] - the upper limit VH and the lower limit VL are calculated as a function of the voltage unbalances of the battery cells detected at step 310 (e.g. , the suggested speed is lower the higher the voltage unbalance between the different battery cells: the suggested speed, for example, could be equal to 90 km / h when the voltage difference is 0.3 V, and equal to 95 km / h when the voltage difference is 0.1 V);

[0032] - the upper limit VH and the lower limit VL are calculated as a function of the power absorbed by the active auxiliary loads estimated at step 312 (e.g., ensuring that the suggested speed range is centered around the minimum of the EPM curve as illustrated in Figure 1 ).

[0033] Once the suggested speed range (i.e., the upper limit VH and the lower limit VL) has been determined, the method comprises a step 316 wherein the vehicle provides the driver with an indication of this suggested speed range. For example, the indication may be visual as illustrated in Figure 4, which shows a (digital) speedometer 40 of a vehicle according to one or more embodiments, wherein a portion 42 of the speedometer (in the example considered here, comprised between a lower limit VL equal to 70 km / h and an upper limit VH equal to 110 km / h) is colored with a different color from the background to highlight the suggested speed range to the driver. Of course, the indication can also be provided to the driver in other ways, for example with an acoustic warning.

[0034] It will be understood that the method 30 can be kept active continuously during the use of the vehicle, such that the limit speed values VH and VL are updated periodically, as one or more of the relevant conditions change.

[0035] As an example, one can think of a case in which the vehicle is travelling on the motorway and the camera (and / or the navigation system, for example if the camera is “blinded”) detects a speed limit of 130 km / h. In the absence of other contributions, the suggested speed range will be represented by a highlighted (e.g., colored) portion 42 of the speedometer which has its maximum VH equal to 130 km / h. Then, depending on possible auxiliary loads activated subsequently, the portion 42 can be reduced by lowering the value of the upper limit VH; for example, if the user turns on only one heated seat there will be a certain additional consumption which will lower the VH value (e.g., from 130 km / h to 100 km / h), while if he or she turns on two heated seats or other additional loads it may be more convenient to lower the VH value to a different value (higher, e.g. 105 km / h). Furthermore, if the grip coefficient estimated at that time indicates poor grip, the upper limit speed can be further lowered: for example, if the vehicle estimates a grip coefficient fj equal to 0.5 then the suggested speed will drop further (e.g., to 90 km / h). Furthermore, if the vehicle detects that the battery is very exhausted, the upper speed limit can be further lowered: for example, the suggested speed can drop further (e.g., to 40 km / h).

[0036] Of course, notwithstanding the principle of the invention, the construction details and the embodiments may vary widely with respect to what has been described and illustrated purely by way of example, without thereby departing from the scope of the present invention, as defined in the attached claims.

Claims

CLAIMS1. A method (30) of calculating a suggested speed range (42) for a vehicle, comprising:- detecting (302) a maximum speed limit in effect on the section of road travelled by the vehicle;- setting (314) an upper limit (VH) of said suggested speed range (42) to a value lower than or equal to said detected maximum speed limit; wherein the method (30) further comprises detecting (308, 310, 312) one or more of the following parameters: i) energy conditions of a traction battery of the vehicle; ii) temperature of one or more cells of said traction battery of the vehicle; and iii) power absorbed by one or more auxiliary loads of the vehicle; and wherein the method (30) further comprises setting (314) said upper limit (VH) and / or a lower limit (VL) of said suggested speed range (42) as a function of said one or more detected parameters to increase the range of the vehicle.

2. The method (30) of claim 1 , comprising:- detecting (302) a minimum speed limit in effect on the section of road traveled by the vehicle; and- setting (314) said lower limit (VL) of said suggested speed range (42) to a value higher than or equal to said detected minimum speed limit.

3. The method (30) of claim 1 or claim 2, wherein said maximum speed limit and / or said minimum speed limit are detected (302) by recognition of a corresponding road sign via processing of images captured by a camera of the vehicle.

4. The method (30) of any of the previous claims, wherein said maximum speed limit and / or said minimum speed limit are detected (302) by satellite localization of the vehicle.

5. The method (30) of any of the previous claims, comprising:- detected detecting (312) the power absorbed by one or more auxiliary loads of the vehicle;- determining, as a function of the power absorbed by one or more auxiliary loads, a target speed value ( V) of the vehicle where a minimumvalue of the energy-per-meter (EPM) of the vehicle is obtained; and- setting (314) said upper limit (VH) and said lower limit (VL) of said suggested speed range (42) so that said target speed value (V) is included between said upper limit (VH) and said lower limit (VL).

6. The method (30) of any of the previous claims, comprising:- detecting (304) a drive mode (MR, GT, SP, CO) currently used by the vehicle; and- setting (314) said upper limit (VH) and / or said lower limit (VL) of said suggested speed range (42) as a function of said detected drive mode.

7. The method (30) of any of the previous claims, comprising:- estimating (306) a value of a grip coefficient (JJ) between the tires of the vehicle and the road; and- setting (314) said upper limit (VH) and / or said lower limit (VL) of said suggested speed range (42) as a function of said estimated grip coefficient (ju), in particular lowering said upper limit (VH) and / or said lower limit (VL) as the estimated grip coefficient (JJ) decreases.

8. The method (30) of claim 7, wherein estimating (306) the value of the grip coefficient (JJ) comprises detecting precipitation and decreasing the value of the grip coefficient (JJ) as the intensity of the detected precipitation increases.

9. The method (30) of any of the previous claims, comprising providing an indication of said suggested speed range (42) to a driver of the vehicle, in particular displaying (316) said suggested speed range (42) on a speedometer (40) of the vehicle.

10. A system for calculating a suggested speed range (42) of a vehicle, comprising:- at least one sensor configured to detect (302) a maximum speed limit in effect on the section of road travelled by the vehicle;- one or more sensors configured to detect (308, 310, 312) one or more of the following parameters: i) energy conditions of a traction battery of the vehicle; ii) temperature of one or more cells of said traction battery of the vehicle; and iii) power absorbed by one or more auxiliary loads of the vehicle; and- an electronic control unit configured to operate according to themethod of any of the previous claims.

11. A computer program product loadable in a memory of at least one processing device and comprising software code instructions which, when the program is executed by said at least one processing device, cause said at least one processing device carry out the method of any of claims 1 to 9.

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