Patent Description:
A heavy-duty vehicle, such as a truck or semi-trailer vehicle, normally comprises a service brake system based on friction brakes. Friction brakes, such as disc brakes or drum brakes, are not capable of prolonged periods of use which may occur when driving downhill for an extended period of time. If the friction brakes are used too intensively, a phenomenon referred to as brake fading may occur. Brake fading is caused by a build-up of heat in the braking surfaces and leads to significantly reduced braking capability. To avoid brake fading, heavy-duty vehicles often comprise auxiliary brakes capable of endurance braking, such as engine brakes and various retarder systems.

Electric machines can also be used to brake a vehicle, i.e., to generate braking torque. The electric machine then acts as a generator which converts the kinetic energy from the vehicle into electrical energy. This electrical energy can be fed to an electrical energy storage system (ESS) such as a rechargeable battery, or to a brake resistor which dissipates the electrical energy as heat.

Electric machines do not suffer from brake fading, but since the total energy absorption capability of the ESS and brake resistor is limited, the electric machine may still not be able to perform endurance braking for prolonged periods of time. Thus, either additional means for braking need to be installed in the vehicle, or the requirements on the electrical energy system of the vehicle must be over-dimensioned to support endurance braking, which is undesired.

Electric machines are normally associated with a limited peak braking torque capability, which means that electric vehicles often comprise friction brakes in addition to the electric machines in order to provide the necessary torque required for, e.g., emergency braking.

<CIT> discloses a type of vehicle brake arrangement based on a combination of an electric machine and an eddy current brake. This arrangement is able to generate more torque compared to the electric machine alone.

<CIT> discloses an industrial truck equipped with an electric travel drive and controls capable of switching the electric travel drive to regenerative operation for braking. Additionally, it discloses an eddy current brake that can be controlled or regulated by the controls during regenerative operation. The controls manage the eddy current brake based on the rpm of the electric travel drive. Furthermore, the controls control or regulate the eddy current brake in a manner such that the braking torque of the travel drive is supplemented at high rpms by the braking torque generated by the eddy current brake.

There is a continuing need for further improvements in braking arrangements for heavy-duty vehicles which are able to provide sufficient braking torque, also for extended periods of time. It is also desired to simplify control of the ESS system on the vehicle.

It is an object of the present disclosure to provide braking arrangements for decelerating a heavy-duty vehicle which alleviate at least some of the above-mentioned issues.

This object is at least in part achieved by a wheel module arranged to generate torque to accelerate and to decelerate a heavy-duty vehicle. The wheel module comprises at least one electric machine arranged for regenerative braking, an eddy current braking device, and an electronic control unit, ECU. The wheel module further comprises a communications port arranged for communication with an external control unit and a power distribution network arranged to connect the electric machine to the eddy current braking device and to a power port arranged to input and to output electrical power to and from the wheel module. The ECU is arranged to obtain configuration data via the communications port indicative of a maximum output power of the power port, and to control the power distribution network to maintain the output power of the power port below the maximum output power by distributing power from the at least one electric machine between the eddy current braking device and the power port.

The wheel module is preferably connected to at least one electrical energy absorption device, which can, e.g., be an ESS, such as a rechargeable battery or a super-capacitor, or a device that dissipates electrical energy, such as a brake resistor, or a combination of ESS and brake resistor. The disclosed wheel module provides regenerative braking for charging an ESS or the like, while, at the same time, taking the limitations of the ESS, and any other electrical energy absorption devices, into account by limiting the amount of output power in dependence of the configuration data. The communications port is connected to an upper layer control device, i.e., external control unit, which can configure a maximum energy output from regenerative braking in real time. The internal control, i.e., the ECU, will then regulate output power to always be below the configured maximum energy output by diverting regenerated energy to the eddy current braking device instead of to the output power port on the module. This reduces requirements imposed on braking resistors and on energy storage systems, or other electrical energy absorption devices, which is an advantage. This also simplifies dimensioning of the overall vehicle electrical system, since a maximum output power from the wheel module can be assumed. The wheel module may also report a braking capability via the communications port in real time, such that an external control unit is aware of the current braking capability of the wheel module at any given time. This capability is a function of the condition of the eddy current device, and the state of the electric machine, e.g., the axle speed of the electric machine.

According to aspects, the electric machine is arranged to generate an increased amount of braking torque, sometimes referred to as peak braking torque, for a limited amount of time. A current generated by the electric machine during that limited amount of time is diverted to the eddy current braking device, thereby increasing a total amount of braking torque. By operating the electric machine at peak torque, the electric machine is able to generate a significantly increased torque, but only for a limited amount of time. The current generated during such torque overload can be diverted to the eddy current brake and thereby obtain a further increase in braking torque. In this case, the communications port can be configured to report the braking torque capability in real-time to the upper layer control. This report may both comprise the torque capability and also the time duration for which this torque can be maintained. Optionally, a rate of decline in braking torque capability can also be reported, which rate of decline can be determined from a model or preconfigured look-up table. Being able to generate high braking torque for a limited duration of time means that emergency braking operations and the like can be performed without additional braking torque from frictions brakes or the like, even for a heavily laden heavy-duty vehicle, which is an advantage. The reported braking capability will of course decrease if this function is used repeatedly in a limited duration of time, but since the vehicle control system becomes aware of the current capability via the reports, this can be accounted for by the vehicle motion management control system.

According to aspects, the wheel module further comprises a local energy buffer, i.e., some kind of ESS, like a battery or a super capacitor. This buffer can serve two purposes. It can even out the output power from the power port such that higher layer charging control systems will receive a more predictable energy output from the device over time with less rapid fluctuations, i.e., a smoothed or low-pass filtered power output. The buffer can also function as a back-up energy source in case the main vehicle energy source should fail for some reason. This back-up energy source can, for instance, provide emergency braking via the eddy current braking device for a limited duration of time in case of main energy source failure. The back-up energy source can also provide a boost power for the eddy current device in case the electric machine is not able to generate sufficient output power, e.g., due to a high axle speed.

According to aspects, the ECU is arranged to control the electric machine and the eddy current braking device to provide a desired wheel slip level, i.e., a local wheel slip control is achieved through coordination of the electric machine and the eddy current braking device. This allows for high bandwidth control that performs with high accuracy and high speed to regulate wheel slip towards a target wheel slip value. The complexity inherent in this type of motion control is largely contained to the wheel module, which simplifies control of the overall vehicle control systems. Also, the functionality can be verified separately since the functions are comprised in a single unit delivered and assembled as one part with well-defined interfaces towards the rest of the vehicle.

According to aspects, the wheel module comprises an additional communications port. This provides redundancy to the control system. Any of the communications port and the additional communications port can be a wireless or a wired communications port.

According to aspects, the ECU is configured to distribute regenerated electrical power from the electric machine between the eddy current braking device and the power port by the power distribution network in dependence of a target deceleration value of the heavy-duty vehicle. This enables a reliable way of decelerating the vehicle and also allows deceleration by the wheel module in excess of the braking capability of the electric machine alone. Thus, the external control unit, which may be a main vehicle motion control unit, may request a braking torque from the wheel module (potentially indirectly as a wheel slip request) in excess of the capability of the electric machine without configuring a split between braking by the electric machine and braking by the eddy current device. This simplifies overall vehicle control.

According to aspects, the ECU is configured to control the distribution of regenerated electrical power from the electric machine between the eddy current braking device and the power port such that a constant baseline torque level is generated by the eddy current braking device. The torque applied by the electric machine is modulated to control wheel slip at a desired wheel slip level. With the eddy current braking device generating a baseline torque level, the electric machine can be used to control wheel slip with low latency, thereby obtaining accurate and fast wheel slip control. This also means that the eddy current device will not interfere in the wheel slip control, which is an advantage.

According to aspects, the electric machine, the eddy current braking device, and the ECU are integrally formed in a single unit. This simplifies vehicle assembly and also provides a simple interface to the combined brake functions of the electric machine and the eddy current device. Also, the integrally formed single unit can be verified as a unit in terms of functionality.

According to aspects, the electric machine is an axial flux electric machine. An axial flux electric machine can be made relatively flat and can therefore be integrated together with an eddy current device more easily, which is an advantage.

There is also disclosed herein a heavy-duty vehicle unit comprising one or more wheel modules according to the discussions above, and an external control unit arranged to control vehicle motion.

There is also disclosed herein a method for decelerating a heavy-duty vehicle, performed by an electronic control unit, ECU, comprised in a wheel module. The wheel module also comprises at least one electric machine arranged for regenerative braking, an eddy current braking device, a communications port arranged for communication with an external control unit and a power distribution network arranged to connect the electric machine to the eddy current braking device and to a power port arranged to input and to output electrical power to and from the wheel module. The method comprises:.

According to aspects, the method further comprises applying an increased amount of torque by the electric machine for a limited amount of time, and diverting a current generated by the electric machine during that limited amount of time to the eddy current braking device, thereby increasing a total amount of braking torque.

According to aspects, the method further comprises controlling the electric machine and the eddy current braking device to provide a desired wheel slip level.

There is also disclosed herein an electronic control unit, ECU, comprising processing circuitry configured to perform a method according to the discussion above.

There is also disclosed herein a computer program comprising program code means for performing a method according to the discussion above when said program is run on a computer or on processing circuitry of an electronic control unit, ECU.

<FIG> illustrates an example heavy-duty vehicle combination <NUM> for cargo transport. The vehicle combination <NUM> comprises a truck or towing vehicle configured to tow a trailer unit in a known manner, e.g., by a fifth wheel connection. Each of the vehicle units comprise means for generating negative torque, i.e., a braking torque to decelerate the vehicle combination <NUM>. The vehicle combination <NUM> comprises wheels <NUM>, <NUM>, and <NUM>. The combination further comprises an ESS <NUM> such as a rechargeable battery, and a control unit <NUM> for, i. , controlling motion of the vehicle combination. Vehicle control will be discussed in more detail below in connection to <FIG>.

Herein, a heavy-duty vehicle <NUM> is taken to be a vehicle designed for the handling and transport of heavier objects or large quantities of cargo. As an example, a heavy-duty vehicle could be a semi-trailer vehicle, or a truck as described above. As another example, a heavy-duty vehicle could be a vehicle designed for use in construction, mining operations, and the like. It is appreciated that the techniques and devices disclosed herein can be applied together with a wide variety of electrically powered vehicle units, not just those exemplified in <FIG>. Thus, the techniques disclosed herein are also applicable to, e.g., rigid trucks and also multi-trailer electric heavy-duty vehicles comprising one or more dolly vehicle units.

The truck, and potentially also the trailer unit, may comprise electric machines for propulsion and regenerative braking. However, most regenerative electric brakes are not capable of generating enough braking torque to perform hard braking, such as may be required during an emergency braking maneuver or the like, where accelerations on the order of -<NUM> to -<NUM> may be required. A heavy-duty vehicle such as the vehicle <NUM> therefore normally comprises friction brakes to complement the regenerative braking by the electric machine or machines.

However, as mentioned above, it is required to be able to brake the vehicle <NUM> as it travels down steep long hills and the like, where friction brakes risk onset of brake fading. Thus, an endurance braking system, such as an engine brake or hydraulic brake system for prolonged periods of braking may be required in addition to the regenerative brakes and the friction brakes. This rather complicated braking system drives cost and also requires extensive servicing.

<FIG> shows an example regenerative braking system <NUM> comprising an electric machine <NUM> coupled to a wheel <NUM>, <NUM>, <NUM>, which could be any wheel in the vehicle combination <NUM>. The electric machine <NUM> is connected to at least one electrical energy absorption device <NUM>, <NUM>, which can, e.g., be an ESS <NUM>, such as a rechargeable battery or a super-capacitor. An electrical energy absorption device can also be a device that dissipates electrical energy, such as a brake resistor <NUM> which converts the electrical energy to heat without providing any useful effect such as braking or energy storage. A brake resistor may also regulate voltage and current levels of the braking arrangement. An electrical energy absorption device may also be a combination of devices that store electrical energy and devices that dissipate electrical energy.

In <FIG>, the electric machine <NUM> is connected to an ESS <NUM>. Electrical energy <NUM> from the electric machine <NUM> generated during braking (moment M) is fed <NUM> to the ESS as long as the ESS can absorb the power. When the ESS is fully charged <NUM> no more energy can be absorbed by it. Furthermore, there may be a limit on maximum current or voltage that can be fed to the ESS when charging. If the ESS cannot accept all energy from the electric machine, surplus energy can be fed <NUM> to a brake resistor <NUM> which dissipates the surplus energy as heat. The braking system <NUM> therefore comprises a switch or power distribution network <NUM>, which is arranged to distribute the generated electrical energy from the electric machine <NUM> between the ESS and the brake resistor. It is appreciated that this device <NUM> can be implemented as a switch arranged to select destination of all of the power from the electric machine, or as a more complicated power electronics network configured to distribute one part of the power to the ESS and another part to the brake resistor. The brake resistor has a maximum amount of power it can absorb since it will eventually get too hot <NUM>. Furthermore, there is normally a peak power capability of the brake resistor, i.e., there may be a limit on maximum current or voltage that can be fed to the brake resistor. The system <NUM> also comprises an external control unit <NUM> arranged to send a braking request to the electric machine <NUM> and arranged to control the switch or power distribution network <NUM>.

If the battery is fully charged and if the brake resistor has reached a maximum allowable temperature, there is no safe way of dispersing the power generated from the electric machine <NUM> during braking. In that case, regenerative braking must cease. This problem can be alleviated somewhat by over-dimensioning the brake resistor, but that may not be sufficient, e.g. if the vehicle <NUM> is travelling down a long slope. For this reason, additional braking means, such as friction brakes, are required. They are also required since, as mentioned, electric machines normally have limited peak braking torque capability. Friction brakes, however, risk onset of brake fading when the vehicle travels down steep long hills and the like.

<FIG> shows an example wheel module <NUM> according to the present disclosure. The wheel module <NUM> is arranged to generate torque M to accelerate and to decelerate a heavy-duty vehicle <NUM> by at least one electric machine <NUM> arranged for regenerative braking. The module <NUM> also comprises an eddy current braking device <NUM> and an electronic control unit (ECU) <NUM>. The wheel module <NUM> further comprises a communications port <NUM> arranged for communication with an external control unit <NUM> and a power distribution network <NUM> arranged to connect the electric machine <NUM> to the eddy current braking device <NUM> and to a power port <NUM> arranged to input and to output electrical power to and from the wheel module <NUM>. The ECU <NUM> is arranged to obtain configuration data via the communications port <NUM> indicative of a maximum output power of the power port <NUM>, and to control the power distribution network <NUM> to maintain the output power of the power port <NUM> below the maximum output power by distributing power from the at least one electric machine <NUM> between the eddy current braking device <NUM> and the power port <NUM>.

The power port <NUM> can be connected to an ESS <NUM> and/or any other type of electrical energy absorption device such as a brake resistor <NUM>. When connected to a plurality of electrical energy absorption devices, the ECU may provide the functionality of the switch <NUM>, but this switch <NUM> can also be provided external to the wheel module. The wheel module <NUM> comprises a communications port <NUM> where an upper layer control device, i.e., an external control unit such as a main vehicle control unit for motion control, can configure a maximum energy and/or power output from regenerative braking in real time, i.e., on a time scale of a few milliseconds up to perhaps a second or longer. The wheel module internal control unit, i.e., the ECU <NUM>, will then regulate output power to always be below the configured maximum energy and/or power output by diverting regenerated energy to the eddy current braking device instead of to the output power port on the module. This reduces requirement on external braking resistors and also on the main traction battery system, which is an advantage.

The external control unit <NUM> is arranged to send a braking request to the wheel module <NUM>. This request is received by the ECU <NUM> via the communications port <NUM>. The ECU then configures the electric machine to be in a regenerative mode where a braking torque is applied to the motor axle, and power is output from the electric machine. During regenerative braking, the electric machine <NUM> generates electric power which is transmitted to the power distribution network. The distribution network is arranged to distribute the generated electric power between electric machine <NUM>, the eddy current braking device <NUM>, and the power port <NUM> in dependence of the ECU, which in turn receives input from the external control unit <NUM> over the communications port <NUM>.

The wheel module <NUM> also reports a braking capability via the communications port <NUM>. This braking capability may change in dependence of the configured maximum output power on the power port. The braking capability may also change in dependence of a state of the eddy current braking device and/or a state of the electric machine. For instance, an overheated eddy current device may result in a reduced reported braking capability. Thus, the external control unit always has knowledge of current braking capability and maximum output power from the wheel module <NUM>. This simplifies overall control of the vehicle also and the management of the vehicle electrical system in general, which is an advantage.

As an example, if a large deceleration value of the vehicle <NUM> is required, the corresponding required negative torque may exceed what can be generated by the electric machine <NUM> alone. A larger fraction of the regenerated electric power may then be directed to the eddy current braking device <NUM>, which will in turn generate a negative torque, resulting in a larger total negative torque than that produced by the electric machine <NUM> alone. This way a very strong braking force can be generated, which is an advantage.

As another example, if the capacity of the energy absorption device <NUM>, <NUM> is insufficient to absorb the regenerated electric power at some point in time, a larger fraction of the regenerated electric power may be directed to the eddy current braking device <NUM> even if the required torque for braking could be produced solely by the electric machine <NUM>. This is achieved by the ECU <NUM> being arranged to control the power distribution network <NUM> to maintain the output power of the power port <NUM> below the maximum output power by distributing power from the at least one electric machine <NUM> between the eddy current braking device <NUM> and the power port <NUM>. Directing the regenerated electric power to the eddy current braking device <NUM> will result in an additional negative torque being generated by the eddy current braking device <NUM>. This serves both to dissipate the excess regenerated electric power and to decrease the negative torque that needs to be produced by the electric machine <NUM>, resulting in less electric power being regenerated by the regenerative braking. This way the specification and requirements imposed on the peak energy absorption capability of the energy absorption device can be relaxed, which is an advantage. Normally, a zero output power can be maintained, at least for some time, in case no energy absorption capability is present external to the wheel module <NUM>, e.g., if the traction batteries are fully loaded and the brake resistor or resistors are over-heated.

The configuration data indicative of a maximum output power of the power port can be configured based on an energy absorption capability of the energy absorption device <NUM>, <NUM>. An energy absorption capability of the energy absorption device <NUM>, <NUM> includes a maximum amount of energy that the energy absorption device <NUM>, <NUM> can absorb without sustaining damage. An energy absorption capability therefore includes a maximum rate of energy absorption by the energy absorption device <NUM>, <NUM>, i.e., a maximum power.

For a battery <NUM>, an energy absorption capability may be determined at least in part by the difference between the current state of charge of the battery <NUM> and the maximum charge of the battery <NUM>. For example, if the battery is fully charged, the energy absorption capability may be zero. There is also normally a limit on the rate at which a battery can absorb energy, i.e., a limit on input power to the battery. For a brake resistor <NUM>, an energy absorption capability may be determined by the power rating of the brake resistor <NUM>, i.e., the amount of power that can be dissipated via the brake resistor <NUM> without causing it to overheat or become damaged. It is appreciated that the energy absorption capability of a device can vary over time, both short-term and long-term. For instance, an already overheated brake resistor will have a smaller energy absorption capability compared to a cool un-used brake resistor, causing variation over time-spans such as tens of minutes or even tens of seconds. A new battery often has better energy absorption capabilities compared to an older more worn battery; thus the energy absorption capability may also range over a time span of months or even years.

The energy absorption device outside the wheel module may comprise a rechargeable battery <NUM>, and the ECU <NUM> may be configured to control the distribution of regenerated electrical power from the electric machine <NUM> between the rechargeable battery <NUM> and the eddy current braking device <NUM> in dependence of a state of charge (SOC) of the rechargeable battery <NUM>. In particular, a larger fraction of the regenerated electrical power may be directed to the rechargeable battery <NUM> if the SOC is low. Conversely, if the SOC is high or the battery is fully charged, a larger fraction of the regenerated electrical power may be directed to the eddy current braking device <NUM>.

The energy absorption device may comprise a brake resistor <NUM> configured to dissipate excess electrical energy from the electric machine <NUM> and to regulate a voltage level of the braking arrangement. That is, the electrical resistance of the brake resistor <NUM> may be selected such that a voltage experienced by other components of the braking arrangement, e.g., the eddy current braking device <NUM> or the energy absorption device <NUM>, <NUM>, is kept at a desired value. To accomplish this, the resistor can be switched in and out according to a configurable duty cycle.

An eddy current braking device <NUM> comprises at least one electrically conductive component <NUM>, which may be in the shape of a disc, and at least one magnet <NUM>. To increase the ability to generate negative torque, and to improve heat dissipation ability, the eddy current braking device <NUM> may comprise a plurality of electrically conductive discs <NUM> attached to a wheel axle <NUM> for generating braking torque. However, a single disc is of course sufficient for generating braking torque by the eddy current braking device. More than one magnet can of course also be used with one or more respective electrically conductive discs, as illustrated in <FIG>.

The electrically conductive discs are made from an electrically conductive material, which is herein considered to be a material with an electric conductivity similar to that of a metal, substantially an electric conductivity above <NUM> Siemens / m. Optionally, the electrically conducting material may be a metal that reacts weakly to magnetic fields, such as copper or aluminum.

The electrically conductive disc or discs <NUM> are arranged such that when an axle <NUM> to which the eddy current braking device <NUM> is attached is rotating, the electrically conductive disc or discs <NUM> are also rotating. This may for example be accomplished by attaching the conductive disc <NUM> directly to the axle <NUM>, or via some form of gear arrangement.

The at least one magnet <NUM> comprises an electromagnet with a conductive coil and optionally also a core comprising a ferri- or ferromagnetic material, for example iron, permalloy, or ferrite. When an electric current is run through the conductive coils a magnetic field is generated in and around the coil according to Ampère's law. The core concentrates the magnetic flux, thereby producing a stronger magnetic field which increases the torque generated by the eddy current device.

The at least one magnet <NUM> is arranged such that when the eddy current brakes are engaged the electrically conducting disc <NUM> is exposed to the magnetic field between the two magnetic poles, with the field lines of the magnetic field substantially perpendicular to the surface of the disc <NUM>. As an example, the magnet <NUM> could be a magnetic circuit, i.e., an electromagnet where the core is shaped to form a loop, and the electrically conductive disc <NUM> could be inserted into an air gap of the magnetic circuit. As another example, two magnets <NUM> could be arranged with the north pole of the first magnet and the south pole of the second magnet facing each other, with the electrically conductive disc <NUM> inserted between the north and south pole.

When the axle <NUM> is rotating and the eddy current braking device <NUM> is engaged, the magnetic field generated by the magnet <NUM> induces eddy currents in the moving electrically conductive disc <NUM> as predicted by Faraday's law of induction. Said eddy currents generate a magnetic field that counteracts the magnetic field generated by the magnet, thereby creating a drag force on the electrically conducting disc <NUM>. The electrons forming part of the induced eddy currents are subject to an electrical resistance when moving through the electrically conductive disc <NUM>, causing some of the energy of the moving electrons to be dissipated as heat. Through this mechanism, the kinetic energy of the electrically conductive disc <NUM> is converted into heat.

When the eddy current braking device <NUM> is not engaged, the electrically conductive disc <NUM> is not exposed to a magnetic field from the magnet <NUM>. If the magnet <NUM> is an electromagnet, the strength of the generated magnetic field depends on the electric current being passed through the conductive coil. In a situation when the eddy current braking device <NUM> is not engaged, the strength of this electric current may be substantially zero. Thus, advantageously, when an eddy current brake is not engaged, no drag resistance or the like is experienced. This is a major benefit compared to standard service brakes (friction brakes such as disc brakes and drum brakes) which are usually associated with some residual applied brake pad force due to not releasing correctly when not applied, generating rolling resistance and heat.

<FIG> shows details of an example ECU <NUM>. The ECU comprises a processing unit, which in turn comprises, i. , a physical layer (PHY) circuit, power management unit (PMU), and memory microcontroller unit (MCU). The processing unit transmits and receives data via the communications port <NUM>. The processing unit is further connected to: a motor power control unit <NUM>, which is connected to the electric machine <NUM>; an eddy current braking device power control unit <NUM>, which is connected to the one or more magnets <NUM> of the eddy current braking device; and a power port power control unit <NUM>, which is connects the power port <NUM> to the motor power control unit <NUM> and the eddy current braking device power control unit <NUM>. These three power control units controls the respective currents and voltages, via the processing unit <NUM>, according to the discussions above.

With reference to <FIG>, the braking torque capability level Tcap of the electric machine <NUM> may generally correspond to a torque level that is sustainable over an extended period of time. An extended period of time could in this context be <NUM> seconds or more. Thus, a sustainable torque level may, e.g., depend on a capacity of the cooling system of the electric machine <NUM>. However, the electric machine <NUM> is also normally associated with a peak braking torque level Tpeak above a braking torque capability level of the electric machine. This peak braking torque level can be maintained by the electric machine for a limited duration of time. The external control unit <NUM> may then be configured to request a braking torque level from the electric machine <NUM> between the peak braking torque level and the braking torque capability level to decelerate the heavy-duty vehicle. A limited duration of time could for example be <NUM> seconds or less.

Applying a braking torque above Tcap will result in the generation of additional electric power. Optionally, the control unit may be arranged to distribute the additional electric power to the eddy current braking device <NUM>. In addition to the braking torque generated by the electric machine, a braking torque will then be generated by the eddy current braking device, resulting in a higher total braking torque. For example, the total peak braking torque Tpeak may approach four times the total continuous maximum braking torque of the electric machine, though only for the limited amount of time during which a braking torque above Tcap can be sustained. This may for example be useful for emergency braking where high torque is required but only for the limited amount of time it takes to stop the vehicle. In other words, the electric machine <NUM> can be arranged to generate an increased amount of torque for a limited amount of time. A current generated by the electric machine <NUM> during such torque overload, i.e., during that limited amount of time, is diverted to the eddy current braking device <NUM> and thereby increasing a total amount of braking torque. In such case, the communications port <NUM> can be configured to report the braking torque capability in real-time to the upper layer control.

To summarize, <FIG> shows a graph <NUM> illustrating braking torque as a function of the angular velocity of the wheel axle <NUM>, or, (at a scaling factor corresponding to the total gear ratio) the axle speed of the electric machine. At low to moderate angular velocities, braking torques up to the braking torque capability level Tcap can be applied for an extended period of time, and braking torques up to the peak braking torque level Tpeak can be applied for a limited time. At high angular velocities, the electric machine <NUM> may become unable to sustain the braking torque, leading to a decrease in braking torque with increasing angular velocity as seen in <FIG>.

A consequence of this decrease is that less electric power is regenerated, meaning that less electric power from the electric machine <NUM> is available to power the eddy current braking device <NUM>. According to aspects, the wheel module <NUM> may be arranged to power the eddy current braking device <NUM> from a different energy source at high angular velocities of the wheel axle <NUM>. This energy source may for example be a battery <NUM>. According to other aspects, the wheel module <NUM> may also be arranged to power the eddy current braking device from a different energy source if the function of the electric machine <NUM> becomes impaired. In other words, the wheel module <NUM> can be fitted with a local energy buffer <NUM>, e.g., some kind of ESS, like a battery or a super capacitor (as shown in <FIG>). The buffer can serve at least two purposes. It can even out the output power from the power port <NUM> such that higher layer charging control systems will receive a more predictable energy output from the device. The buffer can also provide a back-up energy source in case the main vehicle energy source should fail for some reason. This back-up energy source can provide emergency braking via the eddy current braking device for a limited duration of time in case of main energy source failure. The buffer can also be used to boost the torque generated by the eddy current device for limited periods of time, which may be advantageous at very high axle speeds where the power output from regenerative braking may be reduced.

Generally, the ECU <NUM> may be arranged to request power input from an external energy source via the power port <NUM> to boost the braking torque by the eddy current device. This request may be due to an insufficient energy output from the electric machine, or due to failure in the electric machine. An external control unit, such as a control unit implementing a VMM function, may grant the request and provide the requested extra energy to the eddy current device for braking.

According to aspects, the ECU <NUM> of the wheel module <NUM> is configured to distribute regenerated electrical power from the electric machine <NUM> between the eddy current braking device <NUM> and the power port <NUM> by the power distribution network <NUM> in dependence of a target deceleration value of the heavy-duty vehicle <NUM>. According to other aspects, the external control unit <NUM> is arranged to perform a vehicle motion management function comprising force generation and motion support device (MSD) coordination.

<FIG> schematically illustrates functionality <NUM> for controlling a wheel <NUM>, <NUM>, <NUM> by some example MSDs, here comprising the electric machine <NUM> and the eddy current braking device <NUM> integrated into the wheel module <NUM>. The control is based on, e.g., measurement data obtained from vehicle sensors <NUM> such as wheel speed sensors, global positioning system (GPS) sensors, radar sensors, lidar sensors, and also vision-based sensors such as camera sensors and infra-red detectors. An example vehicle motion support device control system is also shown in <FIG>.

A traffic situation management (TSM) function <NUM> plans driving operation with a time horizon of, e.g., <NUM> seconds or so. This time frame corresponds to, e.g., the time it takes for the vehicle <NUM> to negotiate a curve. The vehicle maneuvers, planned and executed by the TSM, can be associated with acceleration profiles areq and curvature profiles creq which describe a desired vehicle velocity and turning for a given maneuver. An example acceleration profile areq comprises the target deceleration value mentioned above. The TSM function <NUM> continuously requests the desired acceleration profiles areq and curvature profiles creq from a vehicle motion management (VMM) function <NUM> which performs force allocation to meet the requests from the TSM in a safe and robust manner. The VMM function continuously feeds back capability information to the TSM function detailing the current capability of the vehicle in terms of, e.g., forces, maximum velocities, and accelerations which can be generated.

Acceleration profiles and curvature profiles may also be obtained from a driver of the heavy-duty vehicle via normal control input devices such as a steering wheel, accelerator pedal and brake pedal. The source of said acceleration profiles and curvature profiles is not within scope of the present disclosure and will therefore not be discussed in more detail herein.

The VMM function <NUM> operates with a time horizon of about <NUM> second or so, and continuously transforms the acceleration profiles areq and curvature profiles creq into control commands for controlling vehicle motion functions, actuated by the different MSDs such as the wheel module <NUM> of the vehicle <NUM> which in turn report back capabilities to the VMM function <NUM>. The different capabilities are used by the VMM function as constraints in the vehicle control.

The VMM function <NUM> performs vehicle state or motion estimation <NUM>, i.e., the VMM function <NUM> continuously determines a vehicle state S comprising positions, speeds, accelerations, and articulation angles of the different units in the vehicle combination by monitoring operations using various sensors <NUM> arranged on the vehicle <NUM>, often but not always in connection to the MSDs.

The result of the motion estimation <NUM>, i.e., the estimated vehicle state S, is input to a force generation module <NUM> which determines the required global forces and moments Fx Fy Mz, V=[V<NUM>, V<NUM>, V<NUM>], and for the different vehicle units to cause the vehicle <NUM> to move according to the requested acceleration and curvature profiles areq, creq. The required global force vector V is input to an MSD coordination function <NUM> which allocates wheel forces and also coordinates other MSDs such as steering and suspension. The coordinated MSDs then together provide the desired lateral Fy and longitudinal Fx forces on the vehicle units, as well as the required moments Mz, to obtain the desired motion by the vehicle combination <NUM>.

By determining vehicle unit motion using, e.g., global positioning systems, vision-based sensors, wheel speed sensors, radar sensors and/or lidar sensors, and translating this vehicle unit motion into a local coordinate system of a given wheel (in terms of, e.g., longitudinal and lateral velocity components), it becomes possible to accurately estimate wheel slip in real time by comparing the vehicle unit motion in the wheel reference coordinate system to data obtained from the wheel speed sensor arranged in connection to the wheel.

A tyre model, can be used to translate between a desired longitudinal tyre force Fxi for a given wheel i and an equivalent wheel slip λi for the wheel. Wheel slip λ relates to a difference between wheel rotational velocity and speed over ground and will be discussed in more detail below. Wheel speed ω is a rotational speed of the wheel, given in units of, e.g., rotations per minute (rpm) or angular velocity in terms radians/second (rad/sec) or degrees/second (deg/sec). A tyre model is a model of wheel behavior which describes wheel force generated in longitudinal direction (in the rolling direction) and/or lateral direction (orthogonal to the longitudinal direction) as function of wheel slip. In "<NPL>covers the fundamentals of tyre models. See, e.g., chapter <NUM> where the relationship between wheel slip and longitudinal force is discussed.

To summarize, the VMM function <NUM> manages both force generation and MSD coordination, i.e., it determines what forces that are required at the vehicle units in order to fulfil the requests from the TSM function <NUM>, for instance to accelerate the vehicle according to a requested acceleration profile requested by TSM and/or to generate a certain curvature motion by the vehicle also requested by TSM. The forces may comprise e.g., yaw moments Mz, longitudinal forces Fx and lateral forces Fy, as well as different types of torques to be applied at different wheels.

The interface between VMM and MSDs capable of delivering torque to the vehicle's wheels has, traditionally, been focused on torque-based requests to each MSD from the VMM without any consideration towards wheel slip. However, this approach has significant performance limitations. In case a safety critical or excessive slip situation arises, then a relevant safety function (traction control, anti-lock brakes, etc.) operated on a separate control unit normally steps in and requests a torque override in order to bring the slip back into control. The problem with this approach is that since the primary control of the actuator and the slip control of the actuator are allocated to different electronic control units (ECUs), the latencies involved in the communication between them significantly limits the slip control performance. Moreover, the related actuator and slip assumptions made in the two ECUs that are used to achieve the actual slip control can be inconsistent and this in turn can lead to sub-optimal performance.

Significant benefits can be achieved by instead using a wheel speed or wheel slip-based request on the interface between VMM and the MSD controller, thereby shifting the difficult actuator speed control loop to the MSD controllers, which generally operate with a much shorter sample time compared to that of the VMM function. Such an architecture can provide much better disturbance rejection compared to a torque-based control interface and thus improves the predictability of the forces generated at the tyre road contact patch.

With reference to <FIG>, the inverse tyre model block <NUM> translates the required wheel forces Fxi, Fyi determined for each wheel, or for a subset of wheels, by the MSD coordination block <NUM> into equivalent wheel speeds ωwi or wheel slips λi. These wheel speeds or slips are then sent to the respective MSD controllers <NUM>. The MSD controllers report back capabilities which can be used as constraints in, e.g., the MSD coordination block <NUM>. One example of an MSD controller is the wheel module ECU <NUM> discussed above, which can be communicated with over the communications port <NUM>.

Longitudinal wheel slip A may, in accordance with SAE J670 (SAE Vehicle Dynamics Standards Committee January <NUM>, <NUM>) be defined as <MAT> where R is an effective wheel radius in meters, ωx is the angular velocity of the wheel, and vx is the longitudinal speed of the wheel (in the coordinate system of the wheel). Thus, λ is bounded between -<NUM> and <NUM> and quantifies how much the wheel is slipping with respect to the road surface. Wheel slip is, in essence, a speed difference measured between the wheel and the vehicle. Thus, the herein disclosed techniques can be adapted for use with any type of wheel slip definition. It is also appreciated that a wheel slip value is equivalent to a wheel speed value given a velocity of the wheel over the surface, in the coordinate system of the wheel.

The VMM <NUM> and optionally also the MSD control units <NUM>, e.g., the ECU <NUM>, maintains information on vx (in the reference frame of the wheel), while a wheel speed sensor or the like can be used to determine ωx (the rotational velocity of the wheel).

The ECU <NUM> of the wheel module <NUM> may be arranged to control the electric machine <NUM> and the eddy current braking device <NUM> to provide a desired wheel slip level, i.e., a local wheel slip control is achieved through coordination of the electric machine <NUM> and the eddy current braking device <NUM>. This allows for high bandwidth control that performs with high accuracy and high speed. The desired wheel slip level can, e.g., be determined from an inverse tyre model.

The VMM function <NUM> may also keep track of the state of charge of the ESS of the vehicle, i.e., the traction batteries or the fuel cell system as well as the current state of any brake resistors. By using the techniques disclosed herein, with reference also to <FIG>, the implementation of the control by the VMM <NUM> is simplified, since the VMM can now configure the ECU <NUM> via the communications port <NUM> with a maximum output power of the power port <NUM>. The wheel module <NUM> then controls the power distribution network <NUM> to maintain the output power of the power port <NUM> below the maximum output power by distributing power from the at least one electric machine <NUM> between the eddy current braking device <NUM> and the power port <NUM>. Thus, the VMM function does not need to handle output powers from the regenerative braking devices in excess of an expected preconfigured maximum level, which level can be configured in real time as a function of the current energy absorption capabilities of vehicle components such as the traction batteries and any brake resistors. The output power from the wheel module <NUM> may also be more stable if the local energy buffer is implemented, since this local energy buffer can be used to absorb short-term fluctuations in power generated by the electric machine.

In case the VMM function configures a very low output power by the wheel module, the reported braking capability of the wheel module may decrease in response. The total braking capability of the wheel module <NUM> may also decrease if the electric machine and/or the eddy current device becomes over-heated.

According to aspects, slip control during endurance braking can be improved by simultaneously using several types of braking, i.e., what is known as brake blending. As an example, the ECU <NUM> can be configured to control the distribution of regenerated electrical power from the electric machine <NUM> between the eddy current braking device <NUM> and the power port <NUM> such that a constant baseline torque level is generated by the eddy current braking device <NUM>. The torque applied by the electric machine can then be modulated to control wheel slip at a desired wheel slip level. With the eddy current braking device <NUM> generating a baseline torque level, the electric machine <NUM> can be used to control wheel slip with low latency. Thus, by using a wheel module <NUM> as discussed herein, the complexity involved in accurate and robust brake blending is shifted to the wheel module, which then provides a less complex interface to the VMM function. As mentioned above, any rapid fluctuation in output power may be smoothed out if a local energy buffer <NUM> is added to the wheel module design.

Vehicle downhill gradeability relates to the ability of a heavy-duty vehicle to drive down long hills at constant cruising speed. The air resistance and the rolling resistance from the road decelerates the vehicle, while the gravitational pull on the vehicle provides accelerating force. Normally, a retarder or engine brake is used to provide endurance braking. However, the disclosed wheel module <NUM> is possible to design so that endurance braking is supported without need for additional retarders, friction brakes, or the like.

To guarantee vehicle downhill gradeability, the eddy current braking device and the electric machine can be dimensioned to support a constant cruising speed, e.g., somewhere between <NUM>-<NUM>/h, during extended downhill driving. To design for downhill gradeability means that the electric machine is dimensioned to provide a continuous negative torque level at a given level and also arranged to distribute the regenerated energy to the eddy current braking device when the energy absorption capability of the energy absorption device is depleted. The eddy current braking device is dimensioned to absorb this energy level. Thus, vehicle downhill gradeability may be guaranteed, at least for a range of driving conditions.

The electric machine <NUM>, the eddy current braking device <NUM>, and the power distribution network <NUM> may be integrally formed as a single unit in the wheel module <NUM>. The wheel module <NUM> comprises a power port <NUM> for feeding and receiving electrical energy to and from the energy absorption device <NUM>, <NUM>. The wheel module <NUM> further comprises a communications port <NUM> by which it can be connected to the external control unit <NUM>. The wheel module <NUM> may comprise an additional communications port. This provides redundancy to the control system. Any of the communications port <NUM> and the additional communications port can be a wireless port.

The external control unit <NUM> may be arranged to send, e.g., a torque request or a wheel slip request as described above to the wheel end module together with an energy absorption capability of an energy absorption device <NUM>, <NUM> that is external to the wheel end module. Within the wheel end module, the requested torque or wheel slip can then be generated by the electric machine <NUM> and the eddy current braking device <NUM>, while, at the same time, the output power of the power port <NUM> is maintained below the maximum output power. This integrated functionality can be verified on the component level and simplifies overall dimensioning of the vehicle electric system.

According to aspects, the electric machine <NUM> in the wheel module <NUM> is an axial flux electric machine. In contrast to a radial flux electric machine, in which the stator forms a substantially cylindrical shell concentric with the substantially circular rotor and the magnetic flux is directed radially between the rotational axis of the rotor and the stator, the magnetic flux in an axial flux electric machine is directed along the rotational axis of the rotor. Both the rotor and the stator in an axial flux electric machine may be thought of as discs, placed next to each other with the axis of rotation of the rotor perpendicular to both discs. During operation, the magnetic flux between rotor and stator will then be parallel to the axis of rotation. Optionally, more than one stator may be used. Axial flux electric machines may be associated with higher power densities and a less complicated manufacturing process compared to radial flux electric motors.

<FIG> illustrates four use cases <NUM> which a heavy-duty vehicle <NUM> must be able to operate in. The vehicle <NUM> must be able to start in slopes <NUM> (startability), even if the vehicle <NUM> is heavily loaded and the road friction is not ideal. The vehicle must also be able to negotiate even steeper slopes at constant velocity <NUM>, e.g., <NUM>/h (positive gradeability). Downhill gradeability performance <NUM> is perhaps even more important, which means that the vehicle <NUM> must be able to limit speed when driving downhill for longer distances (endurance braking). Finally, acceleration and braking capability implies that peak torque requirements, both on positive and on negative torque, must be met by the vehicle MSDs.

The required longitudinal torque can be expressed as <MAT> where mGCW is the vehicle gross combination weight, ax,req is the required acceleration (which is zero or very small for use cases <NUM>, <NUM> and <NUM>), CdAf is the product of air drag coefficient Cd and vehicle front area Af, ρair represents air density, vx is the vehicle speed, g is the gravitational constant, Cr is rolling resistance, and s is a slope percentage between <NUM> and <NUM>.

In uphill driving positive torque scenarios, the terms <MAT> and gCrmGCW must be overcome by the propulsion MSDs, while in downhill scenarios the terms instead help to brake the vehicle <NUM>. This means that the electric machine must be dimensioned to support positive torque sufficient for use cases <NUM> and <NUM>, while the combination of the eddy current braking device and the electric machine must be dimensioned to provide a combined negative torque to support use cases <NUM> and hard braking according to use case <NUM>.

It is appreciated that the vehicle <NUM> will, most likely, comprise several wheel modules <NUM> which will be coordinated to meet torque requirements, as discussed in connection to <FIG> above.

There is also herein disclosed a heavy-duty vehicle unit <NUM> comprising one or more wheel modules <NUM> according to the discussions above and an external control unit <NUM> arranged to control vehicle motion.

The flowchart in <FIG> shows a method for decelerating a heavy-duty vehicle <NUM>, performed by an electronic control unit (ECU) <NUM> comprised in a wheel module <NUM>. The wheel module <NUM> also comprises at least one electric machine <NUM> arranged for regenerative braking, an eddy current braking device <NUM>, a communications port <NUM> arranged for communication with an external control unit <NUM> and a power distribution network <NUM> arranged to connect the electric machine <NUM> to the eddy current braking device <NUM> and to a power port <NUM> arranged to input and to output electrical power to and from the wheel module <NUM>. The method comprises.

In light of the discussions above, it is understood that the application of braking torque can be done in many different ways. For example, braking torque may be applied only by the electric machine <NUM> and all regenerative power is distributed to an electrical energy absorption device <NUM>, <NUM> connected to the power port. In another example, braking torque is applied by the electric machine <NUM> and regenerative current is distributed to the eddy current braking device <NUM>, which therefore also provides braking torque. In yet another example, braking torque is applied only by the eddy current braking device <NUM>, which is powered by an external ESS <NUM> connected to the power port <NUM>, or by an internal back-up energy source <NUM>.

According to aspects, the method further comprises applying S31 an increased amount of torque by the electric machine <NUM> for a limited amount of time, and diverting S32 a current generated by the electric machine <NUM> during that limited amount of time to the eddy current braking device <NUM>, thereby increasing a total amount of braking torque provided by the wheel module <NUM>.

According to aspects, the method further comprises controlling S33 the electric machine <NUM> and the eddy current braking device <NUM> to provide a desired wheel slip level.

<FIG> schematically illustrates, in terms of a number of functional units, the components of an electronic control unit (ECU) <NUM> according to embodiments of the discussions and methods disclosed herein. This ECU <NUM> may be comprised in a wheel module <NUM>. Processing circuitry <NUM> is provided using any combination of one or more of a suitable central processing unit CPU, multiprocessor, microcontroller, digital signal processor DSP, etc., capable of executing software instructions stored in a computer program product, e.g., in the form of a storage medium <NUM>. The processing circuitry <NUM> may further be provided as at least one application specific integrated circuit ASIC, or field programmable gate array FPGA.

Particularly, the processing circuitry <NUM> is configured to cause the ECU <NUM> to perform a set of operations, or steps, such as the methods discussed in connection to <FIG>. For example, the storage medium <NUM> may store the set of operations, and the processing circuitry <NUM> may be configured to retrieve the set of operations from the storage medium <NUM> to cause the external control unit <NUM> to perform the set of operations.

The ECU <NUM> may further comprise an interface <NUM> for communications with at least one external device, such as an electric machine or a gearbox, as well as other control units on the vehicle <NUM>.

The processing circuitry <NUM> controls the general operation of the ECU <NUM>, e.g., by sending data and control signals to the interface <NUM> and the storage medium <NUM>, by receiving data and reports from the interface <NUM>, and by retrieving data and instructions from the storage medium <NUM>.

The functional units of <FIG> may also be comprised in a vehicle control unit <NUM>, such as a control unit for performing one or more of the functions discussed above in connection to <FIG>.

Claim 1:
A wheel module (<NUM>) arranged to generate torque (M) to accelerate and to decelerate a heavy-duty vehicle (<NUM>), the wheel module comprising at least one electric machine (<NUM>) arranged for regenerative braking, an eddy current braking device (<NUM>), and an electronic control unit, ECU, (<NUM>),
the wheel module (<NUM>) further comprising a communications port (<NUM>) arranged for communication with an external control unit (<NUM>) and a power distribution network (<NUM>) arranged to connect the electric machine (<NUM>) to the eddy current braking device (<NUM>) and to a power port (<NUM>) arranged to input and to output electrical power to and from the wheel module (<NUM>),
wherein the ECU (<NUM>) is arranged to obtain configuration data via the communications port (<NUM>) indicative of a maximum output power of the power port (<NUM>), and to control the power distribution network (<NUM>) to maintain the output power of the power port (<NUM>) below the maximum output power by distributing power from the at least one electric machine (<NUM>) between the eddy current braking device (<NUM>) and the power port (<NUM>), and wherein the wheel module (<NUM>) is characterized in that,
the ECU (<NUM>) is further arranged to control the electric machine (<NUM>) and the eddy current braking device (<NUM>) to provide a desired wheel slip level in response to a wheel slip or wheel speed request obtained via communication port (<NUM>) from the external control unit (<NUM>).