Operating a vehicle comprising vehicle retarding subsystem

Abstract

A method of operating a vehicle comprising at least a first vehicle retarding subsystem controllable to retard the vehicle, and processing circuitry coupled to the at least first vehicle retarding subsystem, the method comprising the steps of: acquiring, by the processing circuitry from the first vehicle retarding subsystem, at least one value indicative of current energy accumulation by the first vehicle retarding subsystem; and determining, by the processing circuitry, a measure indicative of a retardation energy capacity currently available for retardation of the vehicle, based on: the acquired at least one value indicative of current energy accumulation by the first vehicle retarding subsystem; a predefined model of retardation energy accumulation by the first vehicle retarding subsystem; and a predefined limit indicative of a maximum allowed energy accumulation by the first vehicle retarding subsystem.

Claims

1. A method of operating a vehicle, comprising: acquiring, by processing circuitry from a first vehicle retarding subsystem, at least one value indicative of current energy accumulation by the first vehicle retarding subsystem; determining, by the processing circuitry, a measure indicative of a retardation energy capacity currently available for retardation of the vehicle, based on: the acquired at least one value indicative of current energy accumulation by the first vehicle retarding subsystem; a predefined model of retardation energy accumulation by the first vehicle retarding subsystem; and a predefined limit indicative of a maximum allowed energy accumulation by the first vehicle retarding subsystem; and determining a measure indicative of a sustainable retardation power provided by the vehicle without accumulation of retardation energy by the at least first vehicle retarding subsystem.

2. The method of claim 1, further comprising: acquiring, by the processing circuitry from a second vehicle retarding subsystem, at least one value indicative of current energy accumulation by the second vehicle retarding subsystem; and the measure indicative of the retardation energy capacity currently available for retardation of the vehicle is further determined based on: the acquired at least one value indicative of current energy accumulation by the second vehicle retarding subsystem; a predefined model of retardation energy accumulation by the second vehicle retarding subsystem; and a predefined limit indicative of a maximum allowed energy accumulation by the second vehicle retarding subsystem.

3. The method of claim 1, further comprising providing, by the processing circuitry, a signal indicative of the retardation energy capacity currently available for retardation of the vehicle.

4. The method of claim 1, further comprising: acquiring, by the processing circuitry from a routing subsystem, a signal indicative of elevation information of the future vehicle route; and determining a maximum allowed speed of the vehicle based on: the measure indicative of the retardation energy capacity currently available for retardation of the vehicle; the signal indicative of the elevation information of the future vehicle route; and a mass of the vehicle.

5. The method of claim 4, further comprising acquiring at least one ambient condition parameter value; wherein the maximum allowed speed of the vehicle is determined additionally based on the at least one ambient condition parameter value.

6. The method of claim 4, further comprising determining a measure indicative of a sustainable retardation power provided by the vehicle without accumulation of retardation energy by the at least first vehicle retarding subsystem; and wherein the maximum allowed speed of the vehicle is determined additionally based on the measure indicative of the sustainable retardation power.

7. The method of claim 4, further comprising providing a signal indicative of the maximum allowed speed of the vehicle.

8. The method of claim 4, further comprising controlling the vehicle to travel with a speed below the maximum allowed speed.

9. The method of claim 1, wherein the at least first vehicle retarding subsystem includes at least one of a friction brake subsystem, an internal combustion engine, a retarder, and an electric propulsion system.

10. A vehicle control unit, for controlling operation of a vehicle comprising at least a first vehicle retarding subsystem controllable to retard the vehicle, the vehicle control unit being configured to: acquire, from the first vehicle retarding subsystem, at least one value indicative of current energy accumulation by the first vehicle retarding subsystem; determine a measure indicative of a retardation energy capacity currently available for retardation of the vehicle, based on: the acquired at least one value indicative of current energy accumulation by the first vehicle retarding subsystem; a predefined model of retardation energy accumulation by the first vehicle retarding subsystem; and a predefined limit indicative of a maximum allowed energy accumulation by the first vehicle retarding subsystem; and determine a measure indicative of a sustainable retardation power provided by the vehicle without accumulation of retardation energy by the at least first vehicle retarding subsystem.

11. The vehicle control unit of claim 10, further comprising a communication interface for providing a signal indicative of the retardation energy capacity currently available for retardation of the vehicle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) With reference to the appended drawings, below follows a more detailed description of embodiments of the invention cited as examples.

(2) In the drawings:

(3) FIG. 1 is a side view of a vehicle according to an embodiment of the present invention, in the form of a truck including at least a first vehicle retarding subsystem.

(4) FIG. 2 is a simplified schematic block diagram of the vehicle in FIG. 1.

(5) FIG. 3 is a flow-chart schematically illustrating a method according to a first example embodiment of the present invention.

(6) FIG. 4 is a flow-chart schematically illustrating a method according to a second example embodiment of the present invention.

(7) FIG. 5 is a flow-chart schematically illustrating a method according to a third example embodiment of the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

(8) FIG. 1 schematically shows a vehicle according to an example embodiment of the present invention, here in the form of a truck 1, including an ICE arrangement 3, an electric propulsion system 5, wheels 11, a friction brake subsystem 13, and a vehicle control unit 15 for controlling operation of the vehicle 1. The electric propulsion system 5 comprises an electric motor 7 and a battery module 9.

(9) The vehicle 1 in FIG. 1 includes three different vehicle retarding subsystems: the friction brake subsystem 13, the ICE arrangement 3, when in retardation mode, and the electric propulsion system 5, when in retardation mode. It should be understood that the vehicle 1 may comprise additional vehicle retardation subsystems, for instance a mechanical energy storage device, such as a fly wheel, and/or a hydraulic energy storage device, such as a hydraulic accumulator.

(10) FIG. 2 is a simplified schematic block diagram of the vehicle in FIG. 1. Referring to FIG. 2, the vehicle control unit comprises a retardation capacity determining block 19, a motion planning block 21, and a vehicle control block 23. As is schematically indicated in FIG. 2, the retardation capacity determining block 19 is coupled to the ICE 3, the electric propulsion system 5, the friction brake subsystem 13, and vehicle sensors collectively indicated by reference numeral 18. Such vehicle sensors 18 may, for example, include sensors for measuring ambient temperature and/or wind speed and/or road surface friction. The motion planning block 21 is coupled to a routing subsystem 17, and the vehicle control block 23 is coupled to the ICE arrangement 3, the electric propulsion system 5, and the friction brake subsystem 13.

(11) The interfaces between the different blocks of the vehicle control unit 15 may, for example, be software interfaces (so-called APIs) or hardware interfaces (e.g. an Ethernet bus or a CAN bus). In other words, the interfaces could either be parts of the interface between ECUs or it can be interfaces between software components.

(12) A first example embodiment of the method according to the present invention will now be described with reference to the flow-chart in FIG. 3, and with continued reference to FIG. 1 and FIG. 2 as indicated.

(13) In a first step S10, the retardation capacity determining block 19 acquires at least one value indicative of current energy accumulation by each of the vehicle retarding subsystems of the vehicle 1. In the example embodiment outlined in FIG. 1 and FIG. 2, the retardation capacity determining block 19 thus acquires such values from each of the ICE arrangement 3, the electric propulsion system 5, and the friction brake subsystem 13. For instance, the retardation capacity determining block 19 may acquire one or several temperature readings from the ICE arrangement 3, the state of charge of the batteries 9 from the electric propulsion system 5, and one or several temperature readings from the friction brake subsystem 13. In addition, the retardation capacity determining block 19 may acquire at least one ambient condition parameter value from the vehicle sensor(s) 18.

(14) Based on the acquired parameter values, the retardation capacity determining block 19 determines, in step S11, a measure indicative of the retardation energy capacity currently available for retardation of the vehicle (VCREC), and a measure indicative of a sustainable retardation power provided by the vehicle 1 without accumulation of retardation energy by the vehicle retarding subsystems (VCRTP).

(15) The determination of VCREC is further based on predefined models of retardation accumulation by the respective vehicle retarding subsystems, and predefined limits indicative of a maximum allowed energy accumulation by the respective vehicle retarding subsystems.

(16) For instance, VCREC may be calculated as the sum of:

(17) Maximum brake heat energy that can be absorbed by friction brakes before they start to overheat (i.e. fundamentally lower braking capability or get damaged).

(18) Maximum brake heat energy that can be absorbed by all prime movers (e.g. internal combustion engine or electric motors) before there is a risk of damage/fundamentally worsened performance.

(19) Maximum brake electric energy that can be stored in battery packs or other electrical energy storage devices.

(20) Maximum brake mechanical energy that can be stored in a mechanical energy storage device, such as a fly wheel before there is a risk of either damage or fundamentally worsened performance.

(21) Maximum brake hydraulic energy that can be stored in hydraulic energy storage devices (such as a hydraulic accumulator).

(22) For instance, VCRTP can be derived as a function of speed. For a certain speed it can be calculated as the sum of: Braking power owing to air-drag on the vehicle combination, calculated at said speed. Braking power owing to rolling resistance of the vehicle, calculated at said speed. Heat dissipation power from all friction brakes, calculated at said speed. Heat dissipation power from all prime movers used also for braking, calculated at said speed.

(23) It should be noted that, for instance air-drag and rolling resistance do not need to be part of the calculation of VCRTP, and that such factors may be taken into account as separate terms.

(24) In the next step S12, the retardation capacity determining block 19 provides a signal indicative of VCREC and VCRTP. In embodiments, this signal may be provided to the motion planning block 21 of the vehicle control unit 15. After step S12, the method may return to step S10.

(25) A second example embodiment of the method according to the present invention will now be described with reference to the flow-chart in FIG. 4, and with continued reference to FIG. 1 and FIG. 2 as indicated.

(26) In a first step S20, at least one value indicative of current energy accumulation by each of the vehicle retarding subsystems of the vehicle 1, and at least one ambient condition parameter value from the vehicle sensor(s) 18 are acquired as described above for step S10 of the flow-chart in FIG. 3. In addition, a signal indicative of elevation information of a future vehicle route is acquired from the routing subsystem 17, by the motion planning block 21 of the vehicle control unit 15 in FIG. 2.

(27) In the next step S21, VCREC and VCRTP are determined as described above for step S11 of the flow-chart in FIG. 3. In addition, the maximum allowed vehicle speed v.sub.max is determined, for example by the motion planning block 21 in FIG. 2.

(28) According to one example implementation, it may be verified that a speed profile is considered as safe based on the following relation:

(29) ${?}_0^{s_{end}}\left(m*a_x+m*g*\sin \left({?}_{\mathrm{slope}}\right)-\frac{VCRTP}{v_x}\right)*ds<\mathrm{VCREC},$
where m is the vehicle combination weight, a.sub.x is desired longitudinal deceleration level, g is the gravitational constant, ?.sub.slope is road slope angle (positive uphill), v.sub.x is the desired longitudinal velocity, the integration variable s is travelled distance, and s.sub.end is an arbitrary distance parameter. The relation may advantageously be verified for several different values of s.sub.end. One important candidate may be to set s.sub.end equal to the length of an upcoming slope. The verified safe speed profile v.sub.x(s) will then define the maximum allowed speed at different points along the route ahead of the vehicle 1.

(30) According to another example implementation, it may be verified that a speed profile is considered as safe based on the following relation:

(31) ${?}_0^{s_{end}}\left(m*a_x+m*g*\sin \left({?}_{\mathrm{slope}}\right)-F_a-F_r-\frac{VCRTP}{v_x}\right)*\mathrm{ds}<\mathrm{VCREC},$
where F.sub.a denotes air-drag force and F.sub.r denotes rolling resistance force. In this example, VCRTP has been determined without taking air-drag and rolling resistance into account.

(32) In the subsequent step S22, a signal indicative of the verified safe speed profile is provided by the motion planning block 21. In embodiments, this signal may be provided to the vehicle control block 23 of the vehicle control unit 15. After step S22, the method may return to step S20.

(33) A third example embodiment of the method according to the present invention will now be described with reference to the flow-chart in FIG. 5, and with continued reference to FIG. 1 and FIG. 2 as indicated.

(34) In a first step S30, values are acquired as described above for step S20 of the flow-chart in FIG. 4.

(35) In the next step S31, a verified safe speed profile v.sub.x(s) defining the maximum allowed speed at different points along the route ahead of the vehicle 1 is determined as described above for step S21 of the flow-chart in FIG. 4.

(36) In the subsequent step S32, the various vehicle subsystems, such as the ICE arrangement 3, the electric propulsion system 5, and the friction brake subsystem 13 are controlled by the vehicle control block 23 of the vehicle control unit 15 to achieve the verified safe speed profile determined in step S31.

(37) It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.